Like the 4-hole bubble pipes, these 3-hole ones were manufactured by several companies. Although I don't know for sure, I believe these also had soap pellets inside the older ones, so they were just "dip and blow."
All the 3-hole ones I have have a metal bottom. One is blank on the bottom; others have U.S., Canadian, and British patent numbers and "Made in U.S.A." impressed in the metal. I think these are the older ones (1950s) at least one may be bakelite. The picture of pipes in bags with headers are probably quite current, and they appear to be all plastic.