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Old 04-08-2010, 01:36 PM   #11
Join Date: Jan 2006
Location: Vermont
Posts: 2,832

The 1398 is likely just a serial number and the "SC" number is a Signal Corps serial number. I'm not sure what the "4 wheeled gear" looks like but it's probably a Signal Corps stamp. Does it have "U.S.A." stamped within the boundaries?

Again, you need to measure the diameter of the bolt hole circle, the circle on which the center of all of the bolt holes sit. If it's 6 inches it's likely for a Hall Scott engine and more likely for a Standard J1. If it's 5 1/4 inches it's more likely an OX5, which was used on a large number of different aircraft, but certainly the JN4D was one of the common ones.
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