Small Queen Question Concerning #37

I am a total noob when it comes to collecting Canada, especially the classics. I have a small accumulation that I am starting to put into an album. I am having an issue in discerning the difference between #37 and #37iii in the Unitrade catalogue. They both state orange red with perfs 11 1/2 x 12. Can anyone help me in telling the difference between the two? I am pretty sure I have just a regular #37, but in being able to figure out the difference between the listings, it may help me in the future with id'ing early Canadian stamps.

Thanks in advance.

#37 is actually perf 12 x 12, 37iii 11-1/2 x 12.

Ahhhhh,ok. I am getting used to the catalogue and it doesn't exactly spell out the 12x12 perf for the original listing. Even the small queen ID table was a little confusing for me. I appreciate the feedback BeeSee