[Ron Ramirez]

For the 1977 model year, the STA-225 was replaced by the STA-235, an all silver-faced receiver with 55 watts per channel, a slight improvement over the STA-225's 50 watts per channel.

So your STA-225 was a leftover from the previous year, obviously never sold until you bought what may have been your local Radio Shack store's last unit of that model.

The STA-2000 made its first appearance in the '77 catalog. It was the first Radio Shack "monster" receiver, 75 watts per channel. I have the later version STA-2000D which made its first appearance in the '79 catalog.

I know all of this only because I looked through the Radio Shack catalog archive:

http://www.radioshackcatalogs.com/

Great reading material for when you have the time to browse.

If you go to the '76 catalog and look on page 21, you will see that Radio Shack offered three different "Everything Systems" (receiver, speakers, turntable) that year featuring the STA-225. RS may have put together different packages in Canada, though.