there were variations within a reference. Eg the very first few 2499s first series cases were made by Vichet. They had a smaller diameter but more elogated lugs than the larger cases made thereafter by Wenger. Another example is the 570 Calatrava. Standard case size was 35mm, but some steel ones were 36 or 36.5mm. These larger steel ones often have multi-tone silver Breguet dials and are highly coveted.