Note:
edition
This is the number of prints in a limited print run, with a fixed number of prints produced on the understanding that no further prints will be produced at a later date.
These prints are signed in pencil in the lower right-hand corner of the print and in the lower-left corner one of the following will appear, 3/30, ap or pp.

3/… is the unique numbered print from the print ‘edition’ and … /30 … this is the total number of prints in the edition.

editions without these markers are usually “open edition prints”, unnumbered, and unsigned.
with this type of print, signatures are usually printed with the image and the printing limited only by the number that can be sold.

The ‘authentic signature’ and ‘limited edition’ print is usually sought after by the collector who understands the value of this investment and is more than happy to pay the extra cost for this type of print.

ap = artist proof
an impression of a print taken in the printmaking process to see the current printing state of a plate while the plate (or stone, or woodblock) is being worked on.
This type of print is a unique collector item especially if it incorporates elements that differ from that of the ‘numbered edition’ and is not just a copy of all the prints in the edition.

pp = printers proof
similar to an artist's proof. These prints are ‘not for sale’ but for the print-maker’s files as proof of their work.