Before the 510 I had a 135, 55, and 29 — all silicone. I ran out of room so I found a custom tank builder (Mr. Guppy in Plano, Texas) that agreed to build it. He consulted with Dow Corning and Pittsburg Glass for a long time before he attempted it. It was heavily Euro braced (not a name used at the time) and cross braced in two places on the top. All tanks at the LFS were silicone. Stainless framed and black putty were antiques, even in the 70"s and were not recommended for salt water. The tank was set up on a custom cut chunk of styrofoam boat dock in Richardson, Texas in 1974. It was moved, by a moving company in 1978 to Lubbock, Texas. I maintained that tank and several others until 1997 when I sold it to a fish store that converted it to fresh water. Interestingly enough it was an air-operated undergravel filter all that time. The pump was a dairy milking unit that sat in the attic over my garage and was plumbed to the living room.
The fish store also bought my fish and I kept track of them for several years after that.
Live rock was not the norm in the 70's. Instead we "decorated" with dead, bleached coral. That was "flower shop" expensive. However, I found a Haitian importer that was going out of business because his supplier in Haiti had been wiped out by a mudslide. He had a large lot full of barrels of bleached coral skeletons that he intended to sell to a chemical company in Fort Worth for pennies a pound. I filled a cargo van full of it for just a couple hundred dollars. Some of the pieces were 30 inches tall.
Check your date on silicone seamed aquariums. This sentence is from Wikipedia — Aquariums: Metal-framed aquariums were still available until the mid-1960s, when the modern, silicone-sealed style replaced them.