I remember us having an old wall mounted phone similar to the one in the 1st picture when I was a kid in rural Tennessee. Turning the crank would signal the operator who would respond with "Number please?", after which we would answer with the 2 digit number (ours was "47" and my grandparent's...
I ordered two different sizes of grade 8 bolts from McMaster-Carr a couple of weeks ago. One box said made in USA, the other said made in Canada. You might try them for whatever you need.
I also have the 2 ton HF fold-up model. I've had it for a couple of years and it's given no problems at all. I did replace the bolts with higher quality ones prior to use.
I agree 100%, Gerry. I'm using 3/4" Type L copper for the main run with 1/2" drops. There is no way I would fool with threaded pipe unless I was being paid by the hour to install it and leakproof it. I wouldn't have either aluminum or plastic air lines in my shop.