You're right regarding age. They are mild steel frame/fork. Pretty heavy. Were not racing bikes back in the day, but more heavy duty neighborhood bikes than Huffy Thunder Roads and Sears badged Murray bmx bikes.
They're not super desirable by bmx collectors, but some people (probably people who had them as kids) do collect them. Yours seems to be in pretty complete original condition right down to the axle end caps.
I'm looking on my phone, so I can't really see, but those look like Ashtabula cranks & stem. Also, if the pedals are KKT, that's a plus. Araya hoops. Probably an ACS or Shimano front hub, Shimano rear?
All in all, it's a solid (and heavy) bike that was decent for banging around the neighborhood.