What replacement balance will I need ?

Those numbers are only used to figure out the length of the metal channel and calibration of the spring. They are not otherwise used for identification. 

In order to figure out what Series you need, we have to use the nylon fittings for reference. You show us the bottom one clearly enough, but we still need to see the top.

In the meantime, take a look at our 15-004 and 15-005. Your bottom fitting is going to be a match for one of these two, I'm just not sure which. The only difference is the depth. Please review our dimensions and let me know what you get.

Once I have those two pieces of information, I'm very confident we can get you the hardware you need.

Thanks for the additional photos. Take a look at our S377-25 balance and see if this is a match. If so, then you can go with the 2440 option.