It's curious that they would use the Westwood name, as that is a very common rim designation, used for single wall, drop centre rims with rolled flanges (i.e. no flat sidewall for caliper brakes) for wired-on tires. The design goes back to the 1890s and was popular through the 1950s on bicycles with coaster brakes and stirrup brakes. While there were some aluminum Westwood rims, they were quite rare and the style was almost invariably made of steel. It's hard to tell by the pictures if these are aluminum or dirty chrome.
I believe that the 243 is the model number. The earliest Weinmann BMX rim that I'm aware of is the 255, which was a 20 x 2.125" dropped centre, dimpled hole, aluminum, BMX rim that goes back to at least 1976. By at least 1983 they had a similar rim, now designated 431. If you assume that Weinmann used a sequentially assigned model number, the subject 243 rims could be late 1970s models and essentially the narrower version of the 255. Let's just hope that they are not true Westwood rims.