We called 'em "Dyna-Flaps." The "excuse" given by RCA at the time of their introduction - circa 1970 - had to do with oil prices/need to conserve oil. In addition to being flimsy, they were prone to other pressing defects, like "bubbles" which, if they could be tracked at all, sounded like a *dull thud* for 3 or 4 revolutions.
Having said all that, some actually sounded pretty decent to very good - - my favorite is ARL 2-0731, which contains both Schubert Piano Trios performed by Rubinstein/Szeryng/Fournier.
Having said all that, some actually sounded pretty decent to very good - - my favorite is ARL 2-0731, which contains both Schubert Piano Trios performed by Rubinstein/Szeryng/Fournier.