Done my best e-bay and web surfing and I'm coming up short.

I have a unmarked 8 day Swiss with a Hebdomas style rear mainspring. I have it timed & running but the spring is weak for sure.

I have it measured @ 55" (aprox) LOA & .110" width & .010" thickness Hole / Hole.

I can cut & add a hole if I have to. I'd hate to have to grind the width down but maybe I have to.

The ones I have seen listed for those are 19" long at most. So I'm not sure there is a current source. So far a tongue end from Timesavers is the closest. It is listed @ .154 / .118 & 34" LOA. That may have to be modified if there is no other choice-

Thanks !