Sorry for my ignorance of Russian scripts, but when I google "Russian Cyrillic alphabet", I see letters that look just the same today. If your informant meant to say that the typeface was old-fashioned, then that means nothing in the traditional world that gave us the "Enfield inch". Heavens, the typeface of the "43" looks old enough to be truly from 1843! But such stamps and letter sets, especially those only used very rarely, would have been in the workplace inventory for decades, and no-one would have been concerned whether the workshop Cyrillic set was in a "modern" typeface. "Just mark it up and send it off mate."
---------- Post added at 05:59 PM ---------- Previous post was at 05:49 PM ----------
An intriguing idea. But have you measured the drop?
Try the following: stand the No.5 upside down on a table, i.e. resting on the foresight "ears" and the backsight. You'll probably have to use one hand to hold the butt. Now measure the height of the toe above the table. Would it fit in that case?