Hope you don't mind me copying a previous reply, but it gives you the information you're after! Searching for "economy series", 73373 or 73473 on here should turn up a bit more info too.

I've written quite a few posts on what I call the "second economy series" watches on the forum, but yours belongs to the "third economy series" and we see those a bit less often. They don't seem to have been made for very long and not in large numbers, in a year when Heuer sales declined notably from the previous year and the vast majority of those sales were the more profitable Carrera and Autavia.

Still, it's a nice way into Heuer ownership as John picked out in his reply - it was me recommending the economy series watches as a Heuer "gateway drug" in an earlier post.

I have actually put an economy table together too - it's with Jeff but has never really been a priority for the site I guess, with all the other changes going on.

Here's an extract of what I wrote about the series your watch comes from:

"The third series appears hot on the heels of the second series in 1971, and is already shown in 1970's Chronograph Identification Manual. This time the watch does have a stainless steel case in all iterations, in a simple cushion design. It would appear to be the economy companion watch to the second generation Carrera at this point, with the previous economy series still on sale and briefly overlapping with these models. Dials have contrast registers and also a contrasting Tachy bezel, as per the 1153 Carreras."

The watches appear to be phased in at the end of 1970 as 1971 model year watches and by the start of 1972 are already being phased out. This short lifetime goes a long way to explaining why we don't see them so often, but there's no reason for them not to be sought after - mechanically, they are the same as a contemporary Carrera, Autavia or Camaro.

Hope that helps a bit! I agree there's not much info around about them.