What Are These

Two stamps, placed on post card at different times (one was in place of a postage due). One on right is deeper green, one on left has very faint greenish tinge to entire stamp, even white parts. Are they the same?

Interesting to see then used side by side. Check the perfs, I think they are different. Notice where the stamps touch, the perfs match up at the top but by the time you get to the middle they don't.
I'd suggest the stamp on right is a 1925 SC552 deep green perf 11 while the one on left is either a #581 1923-26 perf 10 or #632 1927 perf 11x10.5, both green.
Is there a cancel date? That might give a clue.

Joe your best bet is to get a handle on what their perforation measurements are. That will go a long way toward helping you find out if they are the same stamp. Just a suggestion.

Cancel date is December 16th, 1925.

How do I mesure prefs when the stamps are on the card? Is there a see through pref detector for sale?

http://stampparaphernalia.com/Stamp...ti-Gauge.jpg

Voila !