Some pretty good replies

Noel, I do deliberately try to make new tools look tatty, as they're less attractive to magpies, especially if you#ve kicked it around the floor straight after painting!
Anyway....
They're copper pipe swage tools for 15mm 22mm and converting 3/4" to accept 22mm.
By using these simple tools, they obviously save the cost of buying (ouch) couplers/sockets and reduces the potential for leads by half

A company I worked for had a swage tool that had an adjustable head on it, but it was pure luck as to what size you swagged too as there was no way to set it for various sizes, which is what gave me the idea for my set of swage punches.
I made a series of these swage punches until I got the correct diameters as they're now just the right diameter to have a reasonable slip fit of the two pipes without them being too loose or too tight.
The holes are used for tying them together, though on occasions its difficult to pull the swage out, so poke a screwdrive through it and pull.
I don't have dimensions at present, but if they're of interest to anyone I can sort out a drawing. Or if your local and have a chunck of your own material you can also use my lathe to make your own.
I didn't have any new pipe to demonstrate with, but the following images give you an idea of the joining process.