"David Billington" wrote in message
...
Info here
http://www.webster-inst.com/techinfo...r/pipeconn.htm shows G
prefix means Gas thread and is I think the same as BSP.

A search for 19 TPI turned up this reference to 7/16 x 19
http://www.vintagecarparts.co.uk/en/...ipple-details/ .

These guys list a 7/16 x 19 http://www.uni-thread.com/tdcycle.html .
Search was 19 tpi thread, maybe that is close enough for your purpose.

That 7/16-19 will probably work.

Still wish I knew what it's origins were.

Paul K. Dickman