Drum Markings

[grey_ghost]

Hi All,
I have a 61 Series 2 - LWB.
I was wondering what the markings are on my drums?
They look like they could possibly be a date?

PS
I cleaned all 4 drums using an electric drill/wire attachment (outside only)
Then cleaned them / de-greased them.
Then painted them black (2 coats)
Here are a before and after picture!

Regards,
The Grey Ghost

[isuzurover]

IRC 2 of the digits are year of manufacture. E.g. my 1968 ex-mil (so ckd) IIa has drums with '67 on them.