Artillery holster question

[Brent B.]

I have a 1916 dated artillery holster with a unit mark of B A III. On the inside of the flap above the 1916 date is appears to be BERL or SERL but it was very hard to read. The unit mark, date and whatever the other word is are stamped into the holster.

Does anyone have any thoughts on the unit marking and who BERL or SERL might be?

Thanks, Brent B.