Larry,
The PSF mark, with the single pinwheel:

There is also a pinwheel near the Finito stamp that appears elsewhere on the monobloc. But, I'm pretty sure it is the lower level of proof.
I think you have confused the Silver Snipe, imported by Galef, with the BL series guns, imported after 1968 by Garcia. The Snipe guns were all 2 3/4" guns, and all the 20 gauge Garcia BL guns were 3" chamber. That likely explains the higher proof on your gun. The Snipe is a flat spring design, the BL used coils. I'm told that very late in production a selective single trigger was available for the Snipe, however, I've never seen one, and that is in most of forty years of looking, the usual trigger is a non selective single. A few had double triggers.
The short lived BL1 had double triggers. The BL2 had the weird-aunt-locked-in-the attic speed trigger. BL 3s and 4s were single selective trigger.
The Snipes are a different series of guns, with a different importer than the BLs. An interesting side note, Webley bought in-the-white Silver Snipe barreled actions, and stocked and case colored them, selling them as Webleys. There are a few listed on the sites right now, at what I consider stupid money.
I don't actually need another Silver Snipe. But, I would still rather carry it (or, the 30" Webley double for sale right here) over an NID.
Regardless of price.
Best,
Ted