Most Harmony banjos were made in the 50's. They are made of bakelite. I had one and sold it on eBay as soon as I could and is where a lot of junk can be bought. Its unfortunate that a lot of newbies to the banjo world get caught up with banjos that no-one wants. It is advisable to go to a jam, gig or or an expierinced banjo player for advise. There are some good entry level banjos that will get you by with a lot of satisfaction, before you decide to go up market to spending real money.
Harmony banjos were made in the USA through the early 1970s. Harmony banjos from the 1950s on had plastic pots, skin heads and round wood dowel sticks. In 1976, the remaining parts were assembled and dumped on the market under a number of brand names, especially Regal - these had plastic heads..
Most of us refer to a "bottle cap" pot as being made of aluminum with 30 brackets. If this is what you have, then you have a generic Asian made banjo. Harmony is one of dozens (hundreds?) of brand names it could sport.
I bought a NOS Harmony Resotone in the early 70's that had a plastic head. The plastic in the pot was specificaly Bakelite which was a very early plastic and very different than the current Rover brand plastic pots. I've managed to get a very decent sound out of mine but I do wish it had come with the skin head.
Mike is correct about the origin of the "bottle cap" banjos. Exactly which Asian country it came from could be hard to pin down if the "Made In" sticker is missing.
The old Harmony Bakelite/plastic banjos can be made to sound pretty good. A plastic head at proper tension, quality bridge, and light gauge strings makes mine sound as good as some of the better entry-level banjos. They respond to setup like any other banjo. No one should be afraid of buying one of these. For the money, they can't be beat (IMHO)
"I thought I was dancing, until someone stepped on my hand!"
i've been playing a plastic harmony for years, and although i'd jump at another banjo in a new york minute, it's served me just fine on the street, on stage and in recording. it don't sound as sweet as a three thousand dollar banjo, but it's got it's own sound and was worth every penny of the two or three hundred i spent on it!
you might as well give your son a ticket to hell as give him a five-string banjo!