Hello again Steve. This month I have learned much more about perforation errors. Looking through some old Rattlesnake Island Local Post Inc inventory I discovered several perf errors from 1967-1973.
Also, in talking with Portland Stamp Company I have come to the conclusion the stamps from 67-73 were not perforated with a die but used the same kind of 80-100 year old machine Portland Stamp Company uses to apply in-line perf 12's. Roughly 3-5 sheets would be laid in the machine which would apply 1 row of perfs each time and then moved for the next row. This would take 15 motions as there are 5 horizontal, 5 diagonal left, & 5 diagonal right rows. Of course forgeries may exists, however I believe there are many perf errors from 1967-73 that exist. Also, I came across 3 error lists for sale from the 1979 & the 80's from Jacob Kisner New York, NY. His mailing included how they bought a large inventory of sheets from the RILP, Inc. and found the errors throughout the stock.
I started an ERRORS tab and posted the ones I personally found in the RILP, Inc. Inventory I purchased with the company rights. Dave Gill