Identifying Direct Connection Valve Covers

We are in the process of cleaning out one of our storage conexs, and I came across some big block Direct Connection valve covers that I bought back in the early 2000s. The guy I got them from claimed he had them for a "long time" but couldn't remember the year or the decade.

I tried searching for a thread on how to properly identify them, but I couldn't find anything definitive. These have the baffles on the inside. They're fairly heavy. No markings on the inside that I can see.

Any assistance would be greatly appreciated.

20230219_105704.jpg

20230219_105652.jpg

20230219_110324.jpg