Puzzling Old Interlocking Whimsy Carving

I've been living with this one awhile so as to enjoy it--and puzzle over it!-- before parting with it. My pondering was on whether it is actually composed of two tightly interlocking pieces of wood or was just incised on the surface to give that illusion--but I've now learned that indeed this was a carpenter's trick, and so this a carpenter's whimsy.  I love it as a very satisfying physical object (there is absolutely no wiggle between those two pieces; they are forever locked as tight as could be) which--like bottle whimsies--fills one with a sense of wonder at how if could possibly have been achieved! 

3 3/4" t x 1 5/16" x 1 5/16" and in beautiful condition, with nice age and patina, early 20th c. I would guess.