
Anyone who actually know anything about Widgeons knows that all of the 200 model G-44* Widgeons built actually by Grumman were produced during the war (World War II that is) - i.e. between 1940 and 1945. (*And of course, that includes the J4F-1 variants built for the USCG and the J4F-2 variants built for the US Navy.) Immediately after the war, Grumman produced another 76 model G-44A Widgeons with the enlarged and deeper bow section, but Grumman ended production of them by or before 1949. The final 41 Widgeons ever produced were all built by SCAN (as the "Type 30") in Rochelle, France between 1949 and 1952 or so.

Of course, N4453 is one of the SCAN Type 30 Widgeons built in France by or before 1952, serial no. 31 to be exact, so it cannot be a "Grumman" and it cannot be a "1967" anything either. Per 14 CFR 45.13, every aircraft is properly identified based on who actually "built" it, as what, and with its actual date (year) of manufacture - which is not the same thing as date of issuance of a certificate of airworthiness. (That comes into play later....) So, even though it may be "covered" under the same FAA type certificate as the Grumman G-44A (i.e. A-734) N4453 was "built" actually by SCAN as a Type 30 in the 1950 to 1952 time frame, so that makes it a (let's call it) a "1951" SCAN Type 30, but it is NOT a "1967 Grumman G-44A"
Note too that per "Note 5" at the end of TC A-734, each Widgeon built by SCAN as a model "Type 30" is supposed to have a data tag that identifies it as such. Accordingly, the aircraft in question here certainly would not be "legal" if it has some other kind of data tag identifying it as a "Grumman G-44A" for example. Read it for yourself here:
http://rgl.faa.gov/Regulatory_and_Guidance_Library/rgMakeModel.nsf/0/4c4120489ea07a1385256738005ac058/$FILE/a-734.pdf
Once again, as most folks already know, many of the SCAN Type 30 Widgeons were not sold initially and subsequently disassembled and put into storage for many years. It was only after most of those in storage were bought up by companies in the US that they were shipped "across the pond", re-assembled, converted with various American engines such as the 300 hp Lycoming R-680 radials installed on N4453. It was probably at that point in 1967 or so that N4453 was issued its first US certificate of airworthiness, but that is not its "date of manufacture." Also, while it may be possible that it was the "last" Widgeon to be so re-assembled and certified, it is not so likely that the current owner/seller's claim that it is the "last Widgeon ever built" has any merit or validity. In fact, it is much more likely that 10 other Widgeons were "built" or manufactured after it since it is serial no. 31 out of 41 known to have been built by SCAN.
Is any of this significant? Actually yes! Because there are differences between the original Grumman G-44A Widgeons and the French-built SCAN Type 30 Widgeons which are only nominally "copies" of the G-44A; the French SCAN Type 30 Widgeons were built to different, i.e. metric standards in terms of materials and hardware and whereas the original Grumman-built aircraft were all Anodized for corrosion protection in salt water, none of the SCAN Type 30 Widgeons were so Anodized. To me, that in particular is a significant difference, so as I said before - Caveat Emptor!