String suggestion

[mangonboat]

I recently acquired a bit of a one-of-a-kind bow, a 1965 Ben Pearson Golden Sovereign customized lefty Lord / Lady Mercury, with a contoured grip that creates a shelf that is parallel to the index finger, souped up with black fiberglass limb faces, very wide limb bases that taper to narrow tips, 55# @28". There is no serial number or other marking of any kind on the bow beyond the "Golden Sovereign Mercury Cushion" plastic/foil covers over the mercury capsule inserts. The guy I got it from picked it up at a roadside yard sale in upstate New York 15-20 years ago and knows nothing about its origins.
  Ive been shooting it with an endless loop 58" dacron string I salvaged from another older bow and the brace height is perfect, but the serving on that old string is starting to unravel a bit and the bow really needs  a new string. I'd like to consider something to get the best performance out of this bow, maybe something very -low stretch with braided loops,  but at the same time I don't want to unreasonably risk damaging a unique bow. Here are a couple photos of the tips.

Any recommendations, and why?  
 
 

If it was me, I would stick with Dacron!

Bisch

[nineworlds9]

If preservation is prime why not try a custom B55 sting.  Ain't FF but at least an improvement over plain old B50.  Several of our sponsors will whip one up.

[Pat B]

The only difference I've noticed between B-50 and B-55 is a slight thickness difference. Everything else seems the same to me...and Dacron is all I use.

[LBR]

I'd go with B-55.

[LBR]

B-55 is a higher grade of polyester;  less stretch and more durability.  Still stretches like crazy, but a little better than B-50.  Better color selection also.