Sure, Jeff, I'll chime in and corroborate. Secret mark vs no secret mark is easy, the sans secret mark 135 and 146 are red brown.
178-183:

You can see the grid in the background of the 178 whereas the 183's background appears solid. You can see the grid in the background of your stamp. I have three 183s and they all look like that.
From the back, lighted:
