what is this custom mauser?

[SVT-40]

nope, just some symbols.

They are called "proof marks" can you post a photo of them?

[ScottB]

You might also try to get some info over at Mauser Central.

[2shotjoe]

They are called "proof marks" can you post a photo of them?

http://img593.imageshack.us/img593/9458/img20110629194213.jpg

http://img269.imageshack.us/img269/8817/img20110629194221.jpg

they remind me of corn flakes for some reason.

[SVT-40]

The proofs "corn flakes" on the bottom of the bolt handle are Imperial GEW 98 proofs.

http://img593.imageshack.us/img593/9458/img20110629194213.jpg

[Kerplow]

looks like a neat old piece. Try and get a couple good shots of the entire rifle.

[NeuTag]

looks like a neat old piece. Try and get a couple good shots of the entire rifle.

Full clear pictures would help. This is one magnificent rifle. I see the engraving is professional and the gold leaf brings it over the mark. This is one beautiful custom piece. Thank you for posting it.