That is a nice price on a good find. My guess is your line is from the late 40s to early 60s. The line looks basically unused.
The information insert likely has more information than anything you will find online. The recommendation to use your GBF line on a rod that matches an HCH silk line is useful. As a first guess, I would try the line on a rod that fishes well with 6/7 weight lines. Try it with a 5/6 rod or a 7/8 weight rod too. Whatever rod/line combo
you like best is the correct one. If you hate it no matter what rod you use, sell the line for a quick profit. It will be our little secret...
Silk requires more maintenance than modern plastic lines. For the basics on evaluating vintage silk, see
the Over My Waders site. Along with the basic info article, there is an article on
cleaning, stripping, and revarnishing silk lines. Your line looks to be in good shape, but it is possible the varnish is sticky and needs some work.
Tom