I live in UK, and I've never seen a fitting like that.
Some points:
It looks like an [obsolete ?? ] solvent weld type which are seldom used now. Most use the 'Speedfit' type now.
The wide end will not be 3/4". Standard UK sizes for pipe is 15mm or 22mm.
The 1/2" bit is not known here.
UK Pipe threads are designated by the
BORE .... eg 1/8" BSP is 0.383 in. OD by 28 TPI. [ yes, you've read it right, ONE eighth ].
So, taking the nearest to 1/2" thread, 1/4" BSP is 0.520" in. OD by 19 TPI.
A similar fitting is commonly available in copper, but it will almost certainly have a compression connection instead of the internal thread.
EDIT Like the pic. except the pic is 15mm. tube.
Sorry, missed a bit ;
To clarify for those who do not use 'Inch' dimensions ..
in. is inches.
BSP is British Standard Pipe.
TPI Threads per Inch
Hope this helps,
Dave
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