Update: (O.S.C.A.) question now resolved - applied to all 1500 S Cabriolet [118S] and 1600 S Cabriolet [118SA] and [118SB] because it was an OSCA engine design by the Alfieri brothers after they left Maserati. 1200 [118G] and 1500-without-S [118H] and [118K] used Fiat engines.

Been doing some tidying up across our collections of [118~] convertibles according to the following:

1200 Cabriolet [118G] (May 58 - April 63) - haven't done/changed anything apart from completing [118G] codes if missing. Therefore whatever comments and IDs have been made about whether 1200 or 1500 S because of eg bonnet vent size are left as they were.

1500 Cabriolets - a fair bit of sorting into 3 different groups:
(i) 1500 S Cabriolet [118S] (1959 to July 62) - the older shield grille front and bonnet vent. Most of these had (O.S.C.A.) as added info so I've filled it in for all of them
(ii) 1500 Cabriolet (without the S) [118H] (April 63 to April 65) - new wider grille, FIAT shield badge, no bonnet vent, no inset headlights in grille. None of these were entered as (O.S.C.A.) so I haven't added it
(iii) 1500 Cabriolet (again without the S) [118K] (April 65 - Sept 66) - as above but new [118K] code by Fiat for an internal upgrade (more BHP, 5-speed gearbox and other stuff). The only external clue seems to be a new round FIAT medallion in grille.

1600 S Cabriolet (with S in title)
(i) first front - shield grille/asymetric bonnet vent/2 headlights - Oct 62 to April 63 only and now coded [118SA] - a new code for us as all our entries were listed as [118SB]
(ii) new front - wider grille/no bonnet vent/4 headlights with second pair in grille/FIAT shield badge in grille - from April 63, coded as [118SB]
(iii) April 65 - as above but now with round FIAT medallion in grille (plus various internal changes such as 5-speed gearbox, steering column redesign etc) - still apparently [118SB] with no code change listed (unlike the 1500 Cabriolet above which went from 118H to 118K)

There seems to be some confusion about whether these 1600 S (and which out of 118SA and/or 118SB???) should be described as (O.S.C.A.) - I've left the mixture of OSCA descriptions as they are until the question is resolved.

I have not found a way of sorting any of these 1200/1500 S/1500/1600 S from rear views - there are comments about badge formats on some entries, but I'm not brave enough to try - so have left those where they were. But someone more clever could probably do some useful checking....

Also looked at the rare (notchback) Coupés - all ours seem to be entered as 1500 only, but apart from completing some unentered codings as [115C] and making model names consistent, I left them alone. These Coupés include a batch of 1966+ Argentine cars with different bodies - more upright rear cabin. Noted one orphan Argentine 1500 S Cabriolet Concord dated as 1959 - is this correct, and is it really a lonely Billy-no-mates example??

Haven't touched the batch of related Argentine 1969+ Fiat 1600 Sport (fastback) coupés, but they look OK.