Hello Glen3006, welcome!

To get the best response to your question please post it out in a new topic in the regular forum as this area is not read by all at all times.
Penny Reads are fascinating, by the way. Just to warn you, people will want scans of any stamps, especially any you think may be plate 77 which are very rare and very expensive, thus the chances of them being that are very rare.
Always, with stamps, start with the assumption that the stamp is worthless and proceed to prove it is worth something (my idea).
If these are the penny reds I am thinking of, there should be plain numbers hidden away in the side fancy scroll work. Tilt the stamp sideways as the numbers are written to be read sideways. The numbers you see will be the plate number, written on both sides.
This is for the stamps with a letter in all four corners issued from 1858-79. There are stamps with letters in just the lower corners (I think it is) from earlier.
Also, condition of a stamp is everything. Rips, tears, thins, missing perforations (bits that stick out around the edges), creases, not too good centering of the design within the whole stamp, what kind of cancel and how heavy it is, etc, will all have an effect on the perceived value of the stamp to others.
Good luck.