Like many of the old molds zig zag, would have been sold by more than one distributor.
When one goes out of business, another would obtain rights.
In some cases an old mold would become an "open" mold.
Good example is the DiSq, sold by many distributors over the years.

At one time I had a list of every Burt mold and what years, what distributor used them.
It showed when the molds went Non-usable, and when and if a new one was made.
Good example is the Hub. When new one was made, it had minor differences. Hence two different Hub molds. Check your hubs, you should have both if you have several hub mold chips.
I loaned that list to a collector several years ago, and never seen it again,