Can you please tell me what is the replacement part

We have never known channel balances to be made in fraction increments. They are usually made in whole number lengths. And with your stamping being "26 5", that tells us that your balance measures 27" in length. That said, could we have you reconfirm your measurement? It should measure 27" in length. When measuring your balance, make sure you are measuring from metal to metal excluding the nylon fittings. 

Great. See if the S380-27 could work in your balance's place. Measure the depth of the bottom balance shoe, like in the diagram below, and see if this balance is a match for yours. If so, then you can go with a 2650 option. 

Alternate view of 15-005