Oh, Lord - I worked for RS in 80. Inventory was the worst - we closed the store at regular closing time and everyone (including the manager's wife and anyone else we could rope in) just started going from peg to peg counting the merchandise. And this was back when RS sold a LOT of small electronics components, so there were a LOT of pegs! We'd start at midnight and finish around one or two AM. I don't remember how often we did it, but I think it was quarterly. I even dreaded inventory more than Black Friday (actually the SECOND busiest day - Dec. 26 was the busiest).
Oh, and we had to tally up all those tickets written each night and balance that total against the drawer. As someone said, we were selling computers at the time, but it was only the TRS-80 Model II. With only 16K of RAM and a cassette recorder for program and data storage, it was definitely not up to the task of keeping a running inventory.