Just to clarify on the gas line sizes...are you measuring the OD or the ID? Pipe, gas, water etc, is measured on the ID. A 1" OD pipe will be a 3/4" pipe.
This appears to be standard 1 inch T&C line pipe with NPT thread's. I'm sure this schedule 40, I don't know what the exact ID would be. If you were going to any hardware store, and buy a 1 inch steel coupling, it would screw onto this pipe.