Manufacturer Identification

Hey all,

Anyone happen to know the manufacturer for this piping? It is likely from the early 90's. It has 1/2"-TYPE M-HMP-W-MADE IN THE USA-ASTM-B8 printed on the exterior and also 1/2"-TYPE M-HMP-W-MADE IN THE USA stamped on the exterior.

Any possible ideas would be appreciated.

The pictures are from two different runs of pipe in two different homes.

Thanks!