I need to buy 6 balances 2930x photos included

This balance looks like either an S351-30 or S390-30. The only difference between these two balances is the depth of the bottom nylon shoe, or the 'heel-to-toe' measurement, so compare both with your old hardware to see what matches best. See the image below.

That stamp simply tells us the strength of the balance, not its identity. So for your new balance, choose stamp option 2930. 

Comparison of the S351 and S390 balance shoes.