I've used iterations of the Fluke 87 for decades professionally in many segments of the industry (electronics), and consider it to be the best all-around, general purpose DMM on the planet. If I could afford one for my now-basic and infrequent needs at home, that would be my choice - not even a second thought. When I've needed functions / capabilities it doesn't have, I've use others (Flukes) such as 289, clamp current meters, thermocouple meters for critical temperature applications, etc.
Since I can't justify that cost personally, know what I use at home? An Extech. I also use them professionally (industrial applications most recently), and have had excellent results. I was skeptical and even did some side-by-side comparisons with much more expensive, calibrated Flukes, and I was impressed. Great stuff for value / quality at an affordable price. Both Fluke and Extech are good U.S. companies. There's a lot of stuff on the market in 2023 from no-name, johnny-come-lately companies on the other side of the world which I consider likely to be 'junk'; all very attractively priced, of course. From what I can tell, I wouldn't go there. Pick a name you have recognized for a few years and which has a track record (like the 2 above) instead. If one needs to be able to trust anything, test equipment is near the top of the list. If it can't be trusted, it's worth nothing.
If a little careful cleaning (think Deox-It) doesn't help your vintage RS (which is cool), you'll likely need some expertise (which I don't know if you have), and possibly documentation (which might be difficult to find) as well, to go any further with it, and professional repair (if available) is probably not cost-effective at this point.
EDIT: I understand that there are some factory-refurbished Flukes available which might save some good money, and I would likely trust those.
