All these budget rigid 26" MTBs from the late 80's onwards are much of a muchness, IMHO. Who actually made it, or whose brand name is on the frame, is not generally that big a deal, in the case of the gas pipe hi-tensile models at least. Just off the top of my head you might encounter Apollo, British Eagle, Emmelle, Falcon, Gemini, Magna, Muddy Fox, Raleigh, Townsend, Trax, Universal, and probably several more others which I have omitted.
There was a fairly standard generic design "formula" for this genre of bikes, in terms of frame angle geometry, frame material, wheelbase, chainstay length, fork rake, frame tube dimensions, cranksets, freewheels, handlebars & stems, & gear shifters.
Whilst there was a bit of variation in componentry, the general rule of thumb was functional but low-budget, especially in relation to gear mechs and wheelsets. They are not going to stand up well to hardcore off road MTB abuse, but for undemanding use on potholed urban roads, gravel and dirt tracks, not involving racing or performing jumps etc, any of them will do the job, and given at least some basic maintenance, they will continue doing the job year after year.
Fortunately or unfortunately, depending if you want to buy or sell, 26" rigids are very much Cinderella bikes currently, and only tend to fetch low prices, except for the more niche bikes with a retro enthusiast following. Very useful and versatile, but not very desirable or valuable.