Case identification please

The case is a steel “5.56mm” very military in quality, dull dark brown finish, but headstamped .223 which caught my eye.
The .223 is at 6 oclock. At 12 oclock there is a tiny square symbol about 1mm in size. Inside the square is some sort of graphic but it is too badly formed and lacks definition. I can’t read it even with a strong magnifying glass.

As a pure guess without seeing a picture I’d go for Barnaul Machine Tool Plant.

I agree with armourer

It certainly SOUNDS like a Barnaul headstamp; here’s a photo of a 7.62x39 case by them, showing what might be the “square” you’re thinking of:

Yes that looks like it. Thanks for that information everybody. As usual the forum has the answer.
Sorry about the delay in replying. I’ve been helping at the NRA open day at Bisley.
Thanks again