Welcome to the forum Shawn.

The timeframe you give us is accurate and pretty helpful - not always the case, but that's only to be expected after 40+ years! I recognised the watch anyway - we see a fair few of these, it's harder for people to ID them without a helpful series name on the dial. As a consequence, we see more requests to identify these watches, and the preceding and following series, than any others - guess it could be handy to cull all the photos and make a gallery on OTD, but Jeff has his hands full of lots of other changes to the website too.

So let's get down to business. We see these watches in catalogues from 1970 and 1971, initially with a 4-digit reference number and later with 5 digits:

We often refer to them as the "economy" watches, not to denigrate them but to signify that they were usually Heuer's cheapest offerings at the time. These things are relative - you can see in the above 1970 catalogue page that the price isn't significantly less than the similar Carrera. This was normally achieved by using chrome- or gold-plated base metal cases rather than the steel of the Carreras etc, though some of the economy series have steel cases too. The case design is usually somewhat simpler too. This was typically the only area of cost-cutting to achieve that price - the other components, including the movement, are identical to those on the contemporary Carrera.

The two watches pictured top left are what we're interested in here, though you can also look at the adjacent Carrera to see just how similar your watch was to that model. The watch on the left has a chrome-plated case so we should focus on the second left, as that has a gold-plated case. The example pictured is a 73325 T with a white dial, but we note below that there is a model with black dial, 73325 NT. And there we have your watch, a 73325 NT, effectively the dial from the watch on the left in the second left case. So, onto your brother's watch. The 73325 T shown has a white/white dial but we can see from the Carrera next to these that Heuer was getting into contrast registers on the Carrera at this point and the same appears to be true for the 73321/5 models too, with later Ts having white dials with black registers. So 73325 T it is then.

As to repairs, they are certainly possible. The case is gold-plated; it can be cleaned to an extent and even replated if desired (the original plating was 20-micron 16K gold so you might want to achieve the same finish if you did go down that route). However, the watch seems to have developed quite a pleasant patina with age and the effect doesn't appear unattractive to me, so you might want to stick with it as is. The hands and markers would have had luminescent material and would have indeed lit up back in the day. However, the efficacy of lume is limited by a number of factors - early watches used radioactive materials that lost efficiency after a number of years and all lume materials have a tendency to absorb water and break down irrespective of whether they are radioactive or not (don't worry, it's never really harmful except to those who made a career of applying it). Lume can be reapplied so the watch would light up again, but this is a personal choice - I like to keep the watch as original as possible so would steer clear, but plenty of people are happy with a competent relume. Competent is a keyword there, we have seen some horrible relume jobs, so make sure whoever services the watch knows what they are doing if you do go the relume route.

The crown was probably gold-plated originally but as it's being used for both winding and setting the time on a manual movement watch, it's not at all uncommon for the plate to wear through on these. Having the original band and buckle is very desirable indeed.

I haven't seen one of these open that I recall, so I'm not certain on the movement but it will be either the Valjoux 7730 or 7733, both based pretty closely on the venerable Venus 188. The good news is that all of those movements were used extensively in a number of watch brands, so they are well known and understood and parts aren't as scarce as they can be for some movements. The movement definitely needs a service, and to see if the chronograph can be brought back up and running. If you give us an idea of your general location, someone may be able to recommend a good watchmaker to service and repair the watch.

So that should give you a good idea, but feel free to ask any other questions that occur!