423B Red 1914 Washington 2 Cent Help

So here is my situation, I have a very rare 12 x 10 Red Washington Stamp 423b, that has turned into a very extraordinary stamp find.....
1.) First, I would like opinions regarding stamps values if a significant date is postmarked? I understand the Scott Catalogs state that significant dates add value, but who and/or what subject matter increases the value, who decides the value? I'm curious for appraisal purposes.
2.) would a Scott 423b be considered more valuable if it is the earliest known dated postmark?
3.) what Auction Company would be the best to consider hiring for the sale of a Scott 423b?
4.) any opinions on the non perforated top regarding value?
5.) any information regarding the non perforated top?

Any information or opinions are appreciated! Thank you in advance.

Are you absolutely sure this is perf 12x10? From what I see, it would seem virtually impossible for any of the sides to be perf 10. I suspect all sides are perf 12.
Added: The straight edge at the top could indicate that the stamp comes from a booklet pane. Scott 406 was issued in both panes & booklets. As far as I know, that is not true of 423B.

Agree with JJLebbert, your stamp is perf 12x12, thus Scott 406.
Perfs are not counted, they are gauged as how many perfs in 2cm.

justice,
JJ and John are correct. I've attached a photo of your stamp where I've made a copy of the bottom perf row, and compared it to that at the side. The perfs are identically aligned, which means they are the same perforation. In this case they are 12 x 12 and that makes the only option a scott # 406.



Using Photoshop, I simply straightened the orientation of your image, and then added a copy of the bottom perf row to the left side. Sorry, this isn't a rare stamp...

Crickets.

Certainly sounds like them.