Unlike other European tubes which used etched codes to record the date of manufacture of the tubes, Telefunken codes were printed on the glass with the same chalky ink as the labels. If you are fortunate enough to have some Telefunken tubes with labels that are intact, here is an explanation of how to determine when they were made.

	Three letter, two digit date codes From 1930 to 1968, Telefunken used a 2-letter code to identify the date of production. The code is sometimes preceded by the first letter of the factory (“B” for Berlin or “U” for Ulm) and followed by a two digit internal number. For example, the “B kt 01” code for the tube in the photo means that it was made in the Berlin, West Germany, factory on August 1963, and the internal number is 01. Scroll down to see the chart of two letter date codes.
	Two digit date codes Tubes that Telefunken manufactured for export have only the two-letter date code without the factory and internal codes. The letter code can appear in either upper or lower case. Look for it near the bottom of the tube after the “Made in Western Germany” print, centered in the middle of the tube (usually uppercase listed in a column instead of side by side), or near the top of tube after the 12AX7 / ECC83 print. For example, for the tubes in the photo, “fr” = Dec. 1968, “LH” = Dec. 1963, and “pe” = Oct. 1964. Scroll down to see the chart of each two letter date codes.
	Two letter, seven digit date codes, 1958–1978 In 1958, Telefunken began to use a new, more complex code format composed of two letters and seven digits. (The letter formats were also used until 1968, so you may see both.) B  ->  Factory code: “B” = Berlin, “U” = Ulm 9  ->  Last digit of day 2  ->  Tens digit of day 0  ->  Tens digit of month (always zero or one) 6  ->  Last digit of year (1958–1978), tens need to be guessed 9  ->  Last digit of month 01 ->  Internal series number D  ->  Internal batch number (may be missing) For the tube in the photo, the code “B9206901” means that the tube was made in the Berlin factory on September 29th, 1966.

Two digit Telefunken date code chart

The chart below is based on the one that was originally published by Eric Barbour (“Tube Collector” Vol. 2, No. 4). Over the years I have checked the date codes found on our Telefunken tubes with the codes in the chart and found them to be reliable (with a few exceptions—please see the list of “known issues” below for more information). For example, the date codes found on the Telefunken 12AX7s we’ve sold have fallen between 1956 and 1968, which is to be expected for this tube type.

Please note that this chart differs from the Eric Barbour version because it includes corrections to duplicates and missing codes. These corrections are based on the logic of the two letter sequence whenever possible (the sequence was random in 1936–43 and interrupted in 1944–1947). With the exceptions of some apparent confusion between 1958 and 1968 date codes, the corrected dates generally remain within the same year. I’ve listed the corrections and known issues below the chart. Please contact me if you have any questions or further information about Telefunken date codes.

One interesting thing about paying attention to the date codes on Telefunken tubes is the degree of consistency in their production. For example, other than very minor variations (ridges in the top of the bottle, number of holes in the side of the plates, mica styles, etc) the ribbed plate and smooth plate Telefunken 12AX7 construction remained very consistent throughout their 2+ decades of production. (The only anomaly I have encountered is a ribbed plate 12AX7 with copper grid posts—all Telefunkens have steel posts to my knowledge. This tube has an “hk” date code, which would put its production date at Aug. 1950?). 

A ää  11/43 äa  9/67 äk  4/43 äz  6/43 aa  6/35 aA  1/46 aB  2/46 ab  4/31 ac  1/49 ad  7/44 ae  4/32 af  2/49 ag  5/32 ah  7/47 ai  5/31 ak  6/32 al  5/35 am  4/36 an  4/35 ao  3/49 ap  1/45 aq  1/55 ar  1/39 as  2/55 at  3/55 au  6/31 av  4/61 aw  5/61 ax  6/61 ay  7/67 az  8/67 B ba  4/55 bb  10/67 bc  5/55 bd  10/46 be  10/52 bf  6/55 bg  7/61 bh  8/61 bi  9/61 bk  5/44 bl  11/67 bm  12/67 br  5/41 bt  11/52 by  12/52 C ca  7/55 cb  10/49 cc  8/55 cd  9/55 ce  9/33 cf  1/30 cg  1/36 ch  12/49 ci  10/61 ck  6/44 cl  11/49 cm  11/61

cn  12/61 co  7/33 cp  2/30 cq  1/68 cr  5/46 cs  8/33 ct  2/41 cu  2/68 cv  3/68 cw  3/30 cy  10/40 cz  4/41 D da  2/31 db  10/55 dc  11/55 dd  1/62 de  7/30 df  2/36 dg  9/30 dh  12/55 di  2/62 dk  4/38 dl  3/62 dm  1/31 dn  3/31 do  4/68 dp  5/68 dq  6/68 dr  9/39 dt  7/36 du  8/30 dw  8/47 E ea  1/56 eb  10/53 ec  2/56 ed  3/56 ee  4/62 ef  5/62 eg  6/62 eh  7/68 ei  2/34 ek  11/30 el  10/36 em  11/53 en  1/34 eö  3/34 eo  8/68 ep  2/45 eq  9/68 er  10/30 es  12/30 et  9/47 ez  12/53 F fa  1/53 fb  4/56 fc  1/54 fd  5/56

fe  6/56 ff  8/46 fg  7/62 fh  3/40 fi  8/62 fk  4/44 fl  9/62 fm  2/53 fn  10/68 fo  2/39 fp  2/54 fq  11/68 fr  12/68 fu  7/42 fv  10/44 fw  3/54 fx  3/53 fy  2/42 fz  9/41 G ga  4/50 gb  10/51 gc  7/56 gd  8/44 ge  8/56 gf  9/56 gg  10/62 gh  11/62 gi  12/62 gm  5/50 go  10/47 gr  6/50 gt  4/45 gu  1/38 gy  12/51 gz  11/51 H ha  10/56 hb  11/56 hc  7/50 hd  10/33 he  11/33 hf  7/46 hg  10/38 hh  12/56 hi  6/39 hk  8/50 hl  1/63 hm  2/63 hn  3/63 hr  12/33 hu  9/50 I ia  7/37 ib  4/33 ic  5/36 id  6/33 ie  1/57 if  4/53

ig  2/57 ih  3/57 ii  5/40 ik  4/37 il  4/63 im  5/53 in  5/33 io  5/63 ip  4/39 iq  6/63 it  11/47 iu  2/40 iv  6/53 iy  1/43 iz  11/42 K ka  1/44 kb  1/50 kc  4/54 kd  12/46 ke  2/37 kf  9/40 kg  11/37 kh  2/50 ki  4/57 kk  10/41 kl  12/32 km  10/42 kn  5/57 ko  11/32 kp  5/54 kq  6/57 kr  4/42 ks  7/63 kt  8/63 ku  10/32 kv  5/39 kw  6/54 kx  9/63 ky  3/50 kz  11/40 L la  3/44 lb  7/57 lc  8/57 ld  9/57 le  2/33 lf  10/63 lg  11/63 lh  12/63 ln  3/33 lr  6/46 lt  1/33 lx  11/39 M ma  10/57 mb  11/41 mc  1/51 md  11/57 me  3/32

mf  8/42 mg  4/47 mh  12/57 mi  1/32 mk  4/40 ml  1/64 mm  2/51 mn  2/32 mo  2/64 mp  3/64 mv  11/44 mw  6/38 my  3/51 mz  6/42 N na  2/44 nb  1/58 nc  2/58 nd  3/36 ne  3/58 nf  4/64 ng  5/64 nh  6/64 nn  7/39 nr  4/46 O oa  5/30 ob  8/39 oc  4/58 od  5/58 oe  12/34 of  12/47 og  6/58 oh  7/64 oi  1/41 ok  2/38 ol  8/64 om  3/41 on  6/30 oo  12/41 op  9/64 or  11/34 ot  10/34 ou  4/30 öz  5/43 P pa  10/39 pb  7/58 pc  8/58 pd  9/58 pe  10/64 pf  11/64 pg  5/47 ph  12/64 pn  7/34 po  8/36 pr  9/34 pt  6/40

Q qa  10/58 qb  11/58 qc  12/58 qd  1/65 qe  2/65 qf  3/65 ql  3/47 qr  2/47 qz  1/47 R ra  1/48 rb  1/59 rc  2/59 rd  9/44 re  9/32 rf  9/36 rg  10/50 rh  11/50 ri  8/37 rk  8/41 rl  3/59 rm  4/65 rn  12/50 ro  5/65 rp  3/45 rq  6/65 rr  7/32 rs  8/32 ru  11/38 rw  2/48 rx  3/48 rz  1/42 S sa  4/52 sb  4/59 sc  5/59 sd  6/59 se  11/35 sf  5/37 sg  5/52 sh  7/65 si  1/40 sk  12/35 sl  9/48 sm  8/48 sn  8/65 so  7/48 sp  10/35 sq  9/65 ss  3/37 st  12/38 su  3/38 sy  6/51 T ta  8/35 tb  8/40 tc  8/31 td  7/53 te  7/31

tf  7/59 tg  6/47 th  8/59 ti  9/59 tk  10/65 tl  9/35 tm  8/53 tn  9/31 to  11/65 tp  12/65 tq  6/41 tr  7/35 tw  9/53 U ua  11/48 ub  10/59 uc  11/59 ud  12/59 ue  1/66 uf  7/52 ug  12/31 uh  11/31 ui  7/43 uk  8/43 ul  9/38 um  3/42 un  10/48 uo  12/48 up  2/66 uq  3/66 ur  8/52 uv  12/44 uw  9/52 uy  7/41 uz  10/31 ük  3/43 üü  12/43 V va  4/49 vb  1/52 vc  7/54 vd  3/39 ve  1/60 vf  2/60 vg  3/60 vh  6/36 vi  4/66 vk  6/49 vl  5/66 vm  2/52 vn  6/66 vp  8/54 vr  5/49 vs  7/38 vt  3/52 vw  9/54 vz  11/36 W wa  9/37 wb  5/38

wc  4/60 wd  5/60 we  12/39 wf  8/38 wg  8/51 wh  7/51 wi  6/37 wk  4/48 wl  6/60 wm  9/51 wn  7/66 wo  12/37 wp  5/48 wq  8/66 wr  9/66 wt  6/48 X xa  5/34 xb  12/36 xc  10/54 xd  7/60 xe  4/34 xf  9/46 xg  8/60 xh  6/34 xi  9/60 xk  10/66 xl  11/66 xm  12/66 xp  11/54 xr  7/40 xw  12/54 xy  9/42 Y ya  10/60 yb  11/60 yc  12/60 yd  9/49 ye  2/35 yf  1/67 yg  2/67 yh  3/67 yi  5/42 ym  8/49 yn  3/35 yq  12/40 ys  1/35 yt  7/49 Z zb  1/61 zc  2/61 ze  3/61 zf  4/67 zm  5/67 zn  6/67 zu  10/43 zw  5/51 zz  12/42

Corrections

Duplicate dates

• dp - changed from 5/58 (duplicate with od) to 5/68 (previously dq)
• dq - changed from 5/68 (now dp) to 6/68 (previously missing)  
• du - changed from 6/30 (duplicate with on) to 8/30 (previously missing)
  
• eh - changed from 8/58 (duplicate with pc) to 7/68 (previously kx)
  
• eq - changed from 9/58 (now pd) to 9/68 (previously missing)
  
• hl - changed from 3/63 (duplicate with hn) to 1/63 (previously missing)
  
• kx - changed from 9/68 (now eq) to 9/63 (previously missing)
  
• ne - changed from 3/56 (duplicate with ed) to 3/58 (previously missing)
  
• nh - changed from 5/64 (duplicate with ng) to 6/64 (previously missing)
  
• pd - changed from 9/53 (duplicate with tw) to 9/58 (previously eq)
  
• tl - changed from 6/35 (duplicate with aa) to 9/35 (previously missing)
  
• ug - changed from 12/32 (duplicate with kl) to 12/31 (previously missing)
  
• vd - changed from 3/40 (duplicate with fh) to 3/39 (previously missing)
  
• xb - changed from 7/36 (duplicate with dt) to 12/36 (previously missing)
  

Duplicate codes

• ee - 4/61 (duplicate with av) deleted (same code as 4/62)
  
• io - 5/61 (duplicate with aw) deleted (same code as 5/63)
  

Inserted code

• sq - inserted as 9/65 (previously missing)
  

Known Issues

Incorrect Dates
(these date codes were all found on 12AX7 tubes, which were not produced before 1950)

• hf - later code than 7/46
  
• hg - later code than 10/38
  
• hk - later code than 8/50?
  
• mf - later code than 8/42
  
• pn - later code than 7/34
  

Dates that are missing codes

• 8/34 - missing code
  
• 1/37 - missing code
  
• 10/37 - missing code
  
• 2/43 - missing code
  
• 5/45-12/45 - missing code
  
• 3/46 - missing code
  
• 11/46 - missing code
  
• 4/51 - missing code
  
• 6/52 - missing code
  

Codes that are missing dates
(these date codes are common on 12AX7 tubes)

• cq - not listed
  
• gl - not listed
• ho - not listed
  
• ij - not listed
  
• jo - not listed
  
• jq - not listed
  
• tj - not listed
  

Other

• zw = sw?