I cant give an exact dat on those but I can say why they were discontinued. The reason is/was that they do not crimp on as do modern gas checks.    That causes two problems.  One is inaccuracy due to the fact that they can and do part from the bullet indiscriminately.
  The other is a safety issue.  Though this has never happened to me several times customers have told me that the gas check was left lodged in the barrel and the next shot caused a bulged barrel at the point where the gas check was stuck in the barrel.
  I have pondered that possibility and doubted  it but coming from multiple sources have to acknowledge it as a possibility. A few customers have told me they will never ever use a gas checked bullet again for that reason.  For these reasons I stopped using the Lyman/Ideal gas checks many yours ago.  For about the past 20 years we have supplied our gas checked bullets with only Gator Checks. The GC gas checks are advertised as " the checks with bite" and they do crimp on tightly. 
One function of a gas check it to increase the shear strength of the bullet base to be higher than the alloy  alone.  The rifling is turning the gas check where as it might not turn the naked bullet.  Think about it as a stuck bolt made from lead. Put a socket wrench on it (rifled barrel) and it strips before it turns. Increase the shear strength buy adding a crimp on gas check to the base and the socket wrench holds and the bolt turns. If the gas check is not crimped onto the bullet maybe the check will turn but not the bolt.
That is a really simple idea to understand but incomplete. Incomplete because the rifling will actually form a mechanical fit between the check and bullet by pressing grooves through the check and into the bullet just like a bolt head and socket wrench interface, the deeper the rifling depth of your barrel the more positive the interface.
Since nothing in this game of loading ammo is absolute there are other variables involved such as bullet alloy hardness and chamber pressure that can make or break the intended purpose of using a gas check. 
Put quite simply the non crimp Lyman/Ideal gas checks did not work nearly as well as the crimp on type so they were discontinued. Newer Lyman and RCBS crimp on type gas checks I have suspected for a long time are made by Hornady.

sell for scrap  copper is high  art

Interesting, Thanks for all the gas check info  I've been using gas checks for 50 years.  I knew about the flying off in flight deal because in the old Lyman manuals it talked about it. Coming off and staying in the barrel is new to me. I paid a dollar for the lot, LOL. I make most of mine now, only because it keeps me busy on cold days.