need to buy a pair of 26" 2530 balance spring

Thanks for posting. It's a bit tough to see the top fitting in these photos, but if it has the same general shape as the 19-005 top fitting, then this is either an S380-26 or S385-26 Channel Balance, most likely. The difference between the Series 380 and Series 385 is the depth of the bottom nylon shoe, or the measurement from 'heel-to-toe'. See the diagram below for reference. Compare both with your old hardware to see what matches best. In either case, for a stamp option choose 2530.

Comparison of the S378, S380 and S385 balance shoes.