🚀 go-pugleaf

The writer asks how to find the number of patents granted in the 
aggregate or by firm for the US patent class 424.  The writer observes
correctly that none of the online computer databases nor (no big 
surprise here since they come from the same place) none of the CD-ROM
products covers time before 1970.

One sure way to get the answer is to go in person to the Patent Office
in Virginia and physically review the "shoe" containing copies of all
patents in that class.  It is in the public search room there, which is
available to anybody.

Less convenient but just as workable is to go to any of the dozens of 
patent depository libararies, which have on microfilm lists of 
the patent numbers of patents in each patent class, and which also have
microfilm copies of the patents themselves, from which the firm name
may be read.