both of those strop option are great and the owners of the shops are members here. for the record I have made purchases from the invisible edge and have been very satisfied wit the edges on his razors. I have not used the strop shop but they are very well liked and have a great rep for service after the sale.

owning both vintage and new strops, unless you can touch the vintage one before buying you might be investing is more problems like dried out leather, nicks and cracks and pasted surfaces.... NOS vintage strops cost nearly the same as new usually.

jim