I just got my 1312 with the 23J and it's great! I always loved the looks of the 44mm 1950 over the 1940 but hated the thickness. I love how much thinner this 1312 is, measuring 15.7mm, with about half the thickness difference removed from the case and the other half from the caseback. Here it is compared to my 18.1mm thick 312 and 441, which have been replaced and are now for sale. Look at how much lower the lugs sit. I can't wait for Panerai to come out with more of these thinner 1950's, especially a ceramic cased one.