01/31/2008. Remarks by Johan Visschedijk: "The aircraft was built as a Grumman JRF-5 in April 1945 and delivered to the USN as BuNo 87729. It was struck from the inventory in September 1953 and sold directly to the Bureau of Land Management in Alaska and registered as N640.

In 1967 N640 was taken to McKinnon Enterprises in Oregon and covered by a number of Supplemental Type Certificates (STCs) converted with a pair of Pratt & Whitney PT6A-20 turboprop engines and numerous other modifications, including the wrap-around windshield, the retractable wing tip floats, the radar nose, and the "picture" cabin windows. It received its new CoA on July 21, 1967. Another BLM Goose, N642, was converted in 1968.

At this point (and at the time the photo was taken) N640 was still technically a Grumman G-21A, still covered by the original Grumman Type Certificate No. 654, as further explained in photo 6150. Initiated by Angus McKinnon, the company and the FAA referred to it as a "Grumman G-21A Hybrid" or "Grumman G-21A Turboprop", while the media used McKinnon G-21 Turbo-Goose as a designation. The aircraft was sold to Larry Teufel of Teufel Holly Farms Inc. of Portland, Oregon, on October 3, 1996

By 2001 Teufel Holly Farms Inc. was the registered owner of N640, and on May 8th, the company filed notice with the FAA that Grumman G-21A serial B-123 was "disassembled and scrapped", relinquishing the registration to Larry Teufel as an individual. The registration was cancelled on July 6, however, only four days later Larry Teufel filed an affidavit for N640, in which he described it as a McKinnon G-21G, c/n 1201. Although registered as a Grumman/McKinnon G-21G, the aircraft is in fact a amateur-built G-21A put together from salvaged parts.

N640 was registered on July 10, 2001 as a G-21D for the used PT6A-28 turboprops, of which the scoops were rotated upwards to pick up less water during take off, while the use of c/n 1201 is improper. McKinnon used that number in 1958 for the very first four-engined G-21C conversion (from G-21A c/n 1147), c/n 1201, and it ceased to exist in 1960 after it was reconverted into the first and only McKinnon G-21D and given serial number 1251."