"Plate blocks" are blocks of four or larger with selvedge attached showing the number of the plate used to print the stamps.
For this issue, the standard format for collecting plate number blocks includes the printer's imprint and a repeated letter.
These are blocks of 8 (2 rows by 4 columns).
I would ask the postmaster if I could see some full sheets of the 1c and 2c stamps, and possibly return home with one of these:
which catalogs for $900 MNH or better yet two
which catalog $1025 MNH each! So your best investment would be to come back with all 1c stamps,
including two blocks of eight with the plate number, imprint and letter, post office fresh and never hinged.
A never hinged single 1c stamp cats for $60, so your total haul would catalog at $2110.
Nice deal for your ratty old jacket and baseball cap!
Next trip - before you go, buy some beat up Morgan silver dollars at their melt value (struck before 1893!) and bring those along.