oldlugs

I went and looked at it, its as new as I've seen anything from that period. The decals are lifting here and there but otherwise its showroom mint. The tires are Cheng Shin, the dropouts are forged, the bars, seat post, and crankset are all alloy. The front chain rings are steel. The derailleurs are Suntour Sevin GT. The seat is early Avenir, the rear rack is Blackburn MTN. The wheels are Araya with steel spokes and the calipers are MX sidepulls, much like those used on some BMX bikes. Its got a set of Araya branded plastic fenders on it that don't show any signs of being ridden. I would have left with it but its too small for me, I need a taller frame, with a 38" inseam, its hard to get a bike that gives me good leg extension. I was looking at an MTB since I want to ride on a lot of hard packed trails.
I also don't want new, I broke two aluminum frames over the years.
My take is that this bike is made by Giant for Schwinn. I had a later model Sierra that I sold years ago and regretted it as time went on. I paid over $800 for the Sierra new in 1989 and rode it only a few times before moving. The Sierra had cantilver brakes and a chromoly frame but the brakes were its worst feature. The one issue I remember having with it was the brakes dragging and not being worth a dam in the cold or wet.

Its been my experience that the lower end model bikes are tougher models. At 6ft 3" tall and over 300 lbs, super light chromoly and low spoke counts don't work. Big, heavy, and steel is the way to go. Finding one of these that's not been beaten to death or left to rust away in some scrap pile is tough. When they do turn up, they bring top dollar, especially in taller frames.
As I get older, and heavier, I'm pickier as to how well a bike fits me. I've had knee problems since I was a teen, I need a bike that allows me to get almost complete leg extension to ride comfortably. Any less and I irritate the issues with my knees.

The Mesa Runner, Sierra, and High Sierra in those years were all pretty much the same with varied levels of equipment and gears. The High Sierra was full Chromoly.
Personally I prefer the Mese Runner because it has steel chain rings and a heavier frame. I've broken a half dozen frames over the years, all were chromoly road bikes.
The bike I really want is an earlier Sidewinder but finding one of them in a 26" frame is tough. I had one but it was rough. I sold it in barely rideable condition to a guy at work for $400 last summer. He completely restored it and gave it to his son.
The Sidewinder however was a much heavier bike, it used a modified version of the Varsity frame.
I like the MR since it has fenders, and they fit well. Many newer bikes can't mount old school style fenders that really keep a rider dry.

Here's the only pic from his ad