Well, it arrived today, and guess what...
It's a stamp that I purchased, and on the 9th of this month. It was shipped with a USPS tracking number, but it didn't arrive until yesterday, the 23rd. USPS lost all contact with it on the 18th, incidentally. I'm somewhat amazed that it arrived at all. I purchased it from the
ebay seller noted previously within this thread: "bank-notes". They list their location in California, but the stamp was mailed from New Jersey. How about that. Also, I've seen a third location, online, for this seller...England. Oh well, do I really want to know what's up with all that. In any event, I don't think I need to be concerned about this stamp as being "worked over", as I only paid $8.50 for it, plus $3 for the tracked shipping. Upon its arrival, I set about in its conservation, and utilising my enhanced technique; and after the usual cool, soapy bath and a dip in the hydrogen-peroxide. The result is nothing short of fantastic, and most satisfactory...
1904, 5˘ in dark blue, and the foreign-letter rate of the Louisiana Purchase exposition issue...

Before and after, front and back...

This was a great buy, but given my shipping nightmare, and from what I've learned here, I may just pass them by in future.
Alan