I have an old Fuller Ball brass sink faucet from ~1890 --- Peck Brothers, in Connecticut (image attached). I got some replacement Fuller Balls (Don Hooper at Vintage Plumbing; www.vintageplumbing.com), which work great.
BUT, I cannot re-attach the water line, due to the thread on the bottom of the faucet being something old and unusual (see image). I thought it was 1/2" BSSP, but after I got a BSSP/NPT converter, it seems I was wrong (the converter is too loose).
The thread has an OD of ~0.75 inches (~19 mm), with exactly 14 threads per inch; it looks like a parallel thread (no change in OD over 2" length). The OD is, I now see, ~2 mm to small for BSSP G1/2 (I originally thought it was BSSP because J. W. Winco's web site listed G1/2 as having 3/4" OD; Wikipedia says instead that it is ~21 mm). NPT 1/2 is even bigger (OD 0.84 inch).
Can't be metric, can it (being from Peck Bros, in Connecticut, I guess from ~1890; also, how could metric give exactly 14 tpi?)??
Is this some old BSSP-like thread for which there is no solution but to stuff in lots of pipe dope? (Which is how I found it) Or is this an unusual, but known, thread for which I can find an adapter?
P. S. --- The Fuller Ball itself works great! I tried it out (w/ supply line leaking) and it worked well, sealing nicely, and going to full open within ~1/4 turn of the handle.