Identification of BUX10 marking

[aldu]

Hello,

I would like to confirm my interpretation of the marking M1013 on the old BUX10 transistors (TO-3 package) I’m using. I believe M stands for Malaysia and 1013 stands for week 10 of 2013 ; is this correct ?

Thanks !

[Peter BENSCH]

Welcome ​@aldu, to the community!

These devices have been obsolete for so long that the colleagues who still know the details about them are probably already retired. On newer devices, only three digits are used for the date code: WWY, i.e. the calendar week and the last digit of the year. 
If, in your case, ‘1013’ does indeed represent the date code, it may have been specified using two digits at a time back then, so that it could be read as week 10 of the year 2013.

I’m very sorry that I can’t give you a definitive confirmation.

Regards
/Peter

[aldu]

Thank you Peter for your quick response, I understand the difficulty. I am dealing with a very old design on my side and have this kind of issue everyday. Well, my colleagues told me all transistors on our products have the same marking, so at least we know it’s all the same batch.