Help with ID please-- JK studio plate/low bowl

I found this large low bowl (looks like a plate in my photo, but it's about 1 1/2" deep). It is marked with a conjoined JK stamp, and looks like it says "'56" below. Looks like a lot US studio pottery from the 50's but I'm not sure--stamped marks were not common on US studio pottery in the 50's-60's. It is quite well done and 12" diameter. Anyone have a clue?
[img]http://i25.servimg.com/u/f25/15/5url=http://www.servimg.com/image_preview.php?i=79&u=15559699]5/96/99/jk_110.jpg[/img][/url]url=http://www.servimg.com/image_preview.php?i=80&u=15559699][/url]

Are you sure it's 56 that's impressed ? because I would have thought impressed dates on studio pottery would be very unusual.

No, I am not sure, and you are right, it would be unusual. The figures in question are very small and don't show well in the photo (the shadows fell wrong with the flash). Upon closer examination with a jeweler's lupe, I must confess, I can't tell what the heck it is.