Some very welcome news here!
I asked, and Grant has shared a photo of his chassis ID plate with me. I expect he may do so here as well at some point? Maybe not, as the car is apparently sold and maybe he will feel that this decision is up to the new owner? The plate is quite dirty and not easy to read precisely but ...
His car seems to fall into a run of perhaps ten(?) similar chassis that were supplied by Fiat to Abarth. Five of those chassis numbers appear on a somewhat cryptic listing kept by Abarth that I believe documented those cars which were given "Certificato d'Origine", necessary for the generation of Italian paperwork so the car could be registered and used in Italy. I consider those cars on that listing to be "Italian Market" cars. It may be that not all were actually sold in Italy? Regardless, all five of those cars were on this listing as being from May of 1961. At least, that is when they were listed as going to various Italian dealers. The actual completion date for some cars may have been slightly earlier?
Grant's car, although clearly part of that batch of perhaps ten cars, is not on the listing, so is likely to be "non-Italian Market" in my mind. It is also likely to date from a time period very close to May of 1961 but there could be some shift earlier or later depending on the priorities of the day. This is one place where collecting coachbuilding numbers may have particularly strong influences on some assumptions we might make. Allemano numbers appear to have been assigned linearly through time, so we can guess a bit as to when a project might have been initiated. It will not tell us when the car was completed or delivered. Maybe an Allemano roster would tell us more, but none has been found and shared ... thus far.
I am also very interested to learn of "Letzen" and his coupe. Very nice! I hope it does not need the trailer to be moved. This car would be a welcome addition to my research files as well. If it's chassis appears on the listing I have already compiled, I will be able to tell you something perhaps "new" to you about your car. Even if it does not yet appear, it will certainly tell us more about the overall production. Lentzen, I am also interested in the source for the production numbers you quoted. They may come from a listing similar to one which I have compiled but it would seem that you may have more? At the moment, I can identify 24 chassis numbers for what would seem to be similarly configured cars. Maybe yours is a 25th? As with your statement, not all of these are identified precisely as to coachbuilder or their configuration as coupe or cabriolet. There are many blanks to fill and I am sure that there are additional cars out there for which we do not yet know anything whatsoever. Just as Grant's car is completely new without any clue that it existed numerically ... except that it falls into the previously mentioned short run of cars, being now the 7th "find" among what may have been ten or more cars in that number range. And, there is a bit of confusion about one of the cars that is "known". What would life be without some confusion?
I have leads to three cabriolet/spider cars that are not yet identified by chassis number. These could be duplicates for numbers already known and may eventually fill in some histories. Some may also be completely "new" to a numerical listing.
When a bit more is shared, either openly or in private, I will be pleased to share a listing that will be more informative. There are some facts that I wish to check. I am in no rush to get this wrong!
Thanks again to all who have shared and thanks as well to those who will share in the future. More data is welcome. And needed! We have already come a long way from 1994, when I listed only two similar cars by chassis number. What will the next fifteen years' study reveal?