I have the 2614KS rusticated and a 614 smooth. The 2614KS (King Size) (system) is only 2mm deeper than 614. The 604KS is 18mm wide x 45mm deep. I believe the 620 is 38 or 40mm deep.Their shapes do have variations. When I was collecting the 904/914/9004/9005 shape, many of them had different bowl and chamber dimensions. One 904 had a noticeably thicker shank than I'd ever seen on another. The 2 just denotes a system model.
614
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2614
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A zero denotes the four digit era.
404
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4004View attachment 145087
The four digits often have narrower stems as well.
They stopped using 4 digits in 70s and went to three digits. the 1xxx were extra large (now EX) , 2xxx large (King Size) and 3xxx regular normal size. I have read on this site that 18x40 or 20x40 is most popular and most sold size for billiards straight or bent.
I have never encountered a 4xxx until your post. I am not an expert on this just a guy with a couple of Savinelli's trying to figure out what he had. I hope I didn't misstate any facts I may have misunderstood.
Still learning !