Hey there, Gordon! Your windows are admittedly a weird design, but your balances look very similar to our Series 770 channel balance. They have the same terminal clip at the end of the cord and seem to install and function exactly the same way. Look them over and see if you agree.
If I'm reading your post right, you have two pairs of balances, each with their own stamps: the 1917DS and the 2117 stamp. The 1917DS is 19" long and the 2117 is 21" long.
So far so good. That would be our S770-19 and S770-21, respectively.
The problem we have now are those stamps, though. Our Series 770 balances seem to use a totally different rating system than your originals. Your sash weights also seem pretty heavy; the strongest weight option we have for the S770-19 is 19D, which carries only 18 through 21 pounds. For the S770-21, that would be the 21E, which only carries 22 through 26 pounds. Both of these are under the weights you gave, which are 27.5 pounds and 29.5 pounds, respectively.
I think these two balances will have to be custom made with heavy-duty springs. Please give me a little time to look into that and I'll get back to you ASAP as to whether that will be possible.
You also mentioned keys for the sash lock, but that is unfortunately not something we carry.
Please bear with us a little longer as we look into those heavy-duty springs for you!
