Advice needed

Hi Sergey:

I'm not much of a U.S. collector, but my first guess on your stamp would be a corner stamp from a booklet pane of six. Possibly Sc. 634d. Several varieties of this stamp and someone more familiar with it will surely identify it with more certainty, Hochstrasse or Richard, perhaps.

Don

 

Sergey, Don is correct that it's a corner stamp from a booklet pane, either a Scott #554c, 634d or 583a. It's not possible with a scan to definitively determine whether the stamp is flat plate printing or rotary printing as well as whether the stamp is perf. 11 or perf. 11-10.5 or perf. 10. A simple perforation check will tell you not only the perf. but also the printing type.
#554c - perf. 11 flat plate print
#583a - perf. 10 rotary press print
#634d - pert. 11X10.5 rotary press print
I'm guess Don is correct about the number, let us know when you check the perforations.