A lot of cutting work used to be carried out on what would nowadays be considered "inferior" quality blanks.
Producing any sort of blank was expensive and work intensive - they were all used, if at all possible.
It was simply because the technology and chemistry hadn't been refined the way they are now.
Very early on in collecting, my brother and his OH left an Irene Stevens vase sitting on a shelf - at a very, very desirable price - because it had a couple of small bubbles and bits of frit in it they decided it couldn't possibly be "right".)
Now, we know if there's a lot of work done on "inferior" blanks, it's because they're probably genuinely very old.