Can Someone Help Me Identify This First-Day Cover (Or Replica Of First-Day Cover)?

Found when sorting a relative's personal effects. Seems to be too good to date from 1946, and the stamp is enclosed in clear laminate, which suggests far more recent. Plain white envelope, nothing on rear, apart from sealed envelope flap.

Anyone seen one of these before, or can offer any background info?

I've googled a wide range of keywords, but can't find a single image result which matches it.

Here is one that sold on ebay in December for GBP 4.

https://www.ebay.com/itm/395080093895


It is understood that that Hawid mounts were created in 1945 by Hans Widmaier, and this blog entry by Apfelbaum implies that acetate Crystal Mounts were first marketed by HE Harris in the 1950s, so that mounted stamp from 1946 was an early use of such material, not a modern creation as you suggested.

https://www.apfelbauminc.com/blog/p...stamp-mounts

These First Day Covers were created as collectibles and handled carefully outside of the regular mailstream so you do not see the normal wear-and-tear that most normal letters from that era.

The quality of the thick paper used on that envelope that has not faded over the years adds credence that cost was not an object when making these covers. They are a beautiful keepsake of an earlier era, and created in such large quantities that they don't hold much value today from a supply/demand perspective.

Side note, I tried using the Stamp Identifier app to look up the catalog number and came up with a wildly random set of results. Methinks something got lost in translation.



Edit: added sentence about FDCs.

Everything about this screams modern. The mount, the flagging of "mint stamp herewith", the reference to GVI in the imperfect tense, the non-Royal Mail cancel. Pretty, though.

This Windsor first day cancel (other date) popped up on an early 1970s Machin first day cover addressed to Benham.

Everything about the cover cries freemasons.

OK.
I think I will try to refrain from posting here for a while. I have made too many incorrect assumptions recently and don't want to misdirect people with wrong information. Cheers.

The stamps are the 1946 GB peace issue 212d is Scott 264 and the other is Scott 265. Stanley Gibbons Cat. Nos.493 and 494.
I think the GPO of that era would insist on an address written on the envelope. I would be fairly sure that even if stamp mounts were being produced in Germany so soon after the war the British people weren't allowed to conduct business with Germany so soon after the war. Both the latter two comments are partly conjecture and I can't prove the point but I feel sure the thing is not a genuine first day cover. British first day covers of the era are in my limited experience ordinary envelopes with the word first day cover written on the envelope.