Seattle Computer Products developed SCP1 DOS on their 8086 S100 BUS Boards before there was an IBM PC. I bought my first S100 BUS computer in 1983 from the company. I drove from Nebraska to Seattle and spent several days at Seattle Computer being trained. Each board was shipped with manuals that gave enough information you could have built your own boards. It had 128k of ram on two boards and two eight inch floppy disks.
As I recall it was about a year later Seattle made a deal to let MS market the OS.
It was very enjoyable then to be in the computer business. Every one was sharing information and experience.
The Seattle Gazelle had a large RED button too. I learned quickly not to allow children to observe it as it was a well lighted button.
My first computers were Trash 80’s.
I installed a faster Ziglog processor in one off them and 64k of ram. All in the keyboard. It made a monkey out of a PC, but would get hot and hang. I was able to solve that problem by drilling quart inch holes all over the keyboard case and soldering large loops of #10 copper wire to various device mounting bolts and heat sinks.
Your years are off somewhere. Probably by about 3.
The IBM PC came out in late 81. I bought one as an engineering student on a university discount deal in May of 82. I financed it like you would a car (my car was paid for). It was a good investment.