[Guest]

OK, understood. From my understanding, the service testing designation was applied to the original service testing variant of the plane. I don't think it was applied to later variants when changing models. In otherwords, I don't think that they would have made a service testing model since I can't find any evidence of the USAAF having service models made before producing planes like the P-51H or the P-47N. Then again, I remember seeing something about a YP-47M being made. I guess it just depended on the plane. The P-40 went from the XP-40 to the P-40 to the P-40B anyways. Oh well...