Patrick
I have just had a look at Teesdale-Buckell. He first published his book in 1900. In the section on patterns there are many diagrams with tables, detailing amongst other data the length of cartridge used. Whilst the majority are, unsurprisingly, 21/2" in length, there are examples using 23/4" and one of 3".
This would indicate both the availability of longer cartridges at that time, as well as guns chambered for them. I'm afraid all this does is make it even more tricky to date your gun. I appreciate that your question is more concerned with when 23/4" chambered guns became more generally available. Though I have little to back it up, my thought is that would be in the post WWII era.
Tim
