Well I've not seen this type before, in a PV studio pro of 1988. 2 springs and 2 coil frames but only one sping per frame. So on diagonal ends a frame and on the opposing diagonal a taught wire link connecting the "dead" end of each spring. Obviously less mechanical power throughput compared to 2 or 3 coils per frame, offset with more electronic gain presumably. So change of tonal structure? more bass component equivalent to a tank of twice the length? or a longer reverb time? or both?