There have been a number of changes in the way PA has handled their state inspections over the years, and I'm no historical expert on what changed when, but with a combination of fading brain cells and digging around on-line, I can provide some insight.
- Back in 69/70 (at the time of the stickers in question) state inspections were required twice per year and expired on one of four quarterly "cycles". The cycle number is the big number on the sticker and was easily discernible by cops from a distance.
- As far back as I can remember, you were allowed to get your vehicle inspected during a three month window ending on the day your sticker expired. So for example, if your sticker expired at the end of January, you could take your car in for inspection in Nov, Dec, or Jan.
So decoding what I can from the sticker that SteveJ posted as an example...
Prior to the inspection sticker shown here, this vehicle would have carried a cycle 2 sticker expiring at the end of Jan 69. The punched out date at the bottom of the sticker shows this vehicle was inspected on Nov 17, (1969), which is during the three month window leading up to the end of cycle 2. A car due at the end of cycle 2 could taken in for inspection during Nov, Dec, or Jan.
The current inspection expires on June 31, 1970 which is the end of cycle 4.
I believe the inspection station number to which the sticker was issued is the ID dot coded at the top of the sticker. If that's the case, then this sticker was originally issued to station A122 (whoever that is).
As for the reference to the PA Department of Revenue, that's who got the fee for the cost of inspection. Even today, when you're sending the check to pay for your yearly license plate registration, you make the check out to the PA Dept of Revenue. In the case of inspections, the station buys the stickers from the state and then the station sells them to the customer. it's just where the money collects at the state level.
Some other neat details and pics available here: http://www.bufs-plates.com/windshield/pennsylvania/pa-ws-1969-1983.html
Did I ever tell you that I've got my PA state inspection mechanics license? Never officially inspected a vehicle, but I took the certification tests and have carried the license for quite some time. The mechanic owns the license, but the station owns the stickers. A certified mechanic working for an authorized station is who performs the inspection, and that's not me.