Thanks for the further input. Your interest is much appreciated.
Up to about 1951 the patent would have been still pending, so any discussion was unlikely. There was also the litigation with Trix at this time.
Peco's Patent 605283 was approved 20 Jul 1948, which was some time if not years before any royalties would be paid.
My Uncle's Patent 617544 was approved 8 Feb 1949.
PECO was set up in 1946, the first advert appearing in the Sep MRC, "Introducing PECO the little name with the big surprises". The first product was Peco-way. Following adverts have Peco apologising for non-delivery until spring 1947 when things had obviously settled down. As for the coupling, the patent was first applied for on 4 Dec 1945 with the amendment stage completed 10 Jul 1946.
So, there was a considerable gap until there's evidence of a tie-up between Peco and Meccano in 1951. That's the context that I'm working in.
Meccano announced their HD relaunch in the Meccano Magazine for Dec 1947 (I've attached a scan - I hope!), following adverts showing there was restricted production, by order to the Govermment.
That first Meccano advert showed the EDG7 Tank Goods Set train set with a Peco-like coupling on the front end of the 0-6-2T, but the one photograph I've seen claiming to be of a 1949 version of such a loco shows that in fact it differs from the Peco design.
Peco didn't announce their coupling in the Sep 1950 model mags.
So, the implication is that Meccano used a similar design but not the Peco design. Given that both Peco and my uncle's Patent were for the same invention (as far as toy vehicles were concerned, as opposed to full size vehicles which my uncle's also covered), I can only conclude that Meccano were using their design to my uncle's Patent. He sold the rights of his Patent to Meccano. And the scene is set for subsequent events.
Even the above isn't a watertight chronology. But if Meccano were using Peco's coupling from the start, why would there be an argument in later years? Since there had been litigation between the holders of two patents, one Pritchard and the other my uncle, I don't give too much credence to one side's story over the other's (either way). That's why I need to see hard evidence. My prejudiced view is that Pritchard was well-known in being litigious and my uncle really couldn't be bothered with the shouting because this was his hobby and he had a 'real-world' business to run.
By the way, acquiring the final Patents themselves is easy - just use Google Patents. Getting the prior versions as they went through the appoval process is less easy - I researched them on microfilm at The Mitchell Library in Glasgow, unfortunately in the days before digital cameras and before I knew quite what I was looking for. All my references to adverts are from the magazines themselves in my possession. The web site you cite has two relevant Patents - I've actually got details of another six worldwide, including Argentina of all places, and images of four of them, the numbers all taken from the box of my 2-6-4T!
I'd be very interested in seeing the demo and mock-up. I notice Pathé news covered at least two demo HD layouts 1947, but the film was far too grainy to make much out.
It's probably a red-herring by a certain Ralph L Watson (no relation) has US Patent 2631240 filed 25 Mar 1949, approved 17 Mar 1953, which looks like a real buckeye in the style of Kadee. He cites 605283. How similar is this patent to what you describe?