ANH wasn’t released on video until 1982, so what you saw in 1981 could have been a bootleg tape or something especially made for military use, which leaves the crawl question up in the air. The first theatrical reissue with the Episode IV crawl was in April 1981.

Can you recall if the tape itself had any markings? Back in college, the tv station I slaved at used to get donations of old tapes made for Navy bases we could reuse. (Mostly late 70’s early 80’s tv shows, all erased before they got to us though.) They were made of blue plastic and had a “U.S. govt’ property” stamped on them in gold on the side.