If I go out to look at an interesting steam system I always bring my pipe caliper along. There are a lot of oddball pipe sizes on those older systems. I ran into 3-1/2" and 7" pipe and fittings a few times but they never threw me because I had this great tool along. I just pushed it up against the pipe until it stopped and then read the pipe size on the scale. Simple is good.
I find it especially helpful on jobs where the pipes are covered with insulation. I carefully cut a slit in the insulation with my knife and slide the pipe caliper into the space. When I pull it back out, I know exactly what we have here. You need to know the pipe size if you're balancing the venting rate of any steam system. And balancing that venting rate is the key to balancing the steam distribution.
The pipe caliper we have to offer is made of steel and it's made in America. It reads iron pipe sizes from 1/4" to 12" and copper tubing from 3/8" to 6". That should cover most everything you'll see out there. This is a high-quality tool, designed to last a lifetime. And if you're not completely satisfied with it, just send it back and we'll give you a full refund. But I think you're going to be glad to have it handy. I sure am.