Vietnam Air Losses by Chris Hobson shows the jet was F-100F 56-3954. If the plane was on the 612th's roster it would have this tail marking: large HS in white (or very pale gray) and in smaller white the numbers 954. Just to the left of the white numbers would be the even smaller black lettering AF over 0-63.
Henk Sharringa's web site shows the plane was assigned to the 35th TFW at Phan Rang (no squadron given) and transferred to the 416th TFS on the very day it was lost, and then assigned back to the 612th TFS at Phan Rang that same day. That totally confuses the possible answers to your question
Typically an F-100 operational squadron would only posses two F-100F models. Misty's use of at least 4 per day would put a strain on the wing's use and maintenance of them. So Misty would use any F model that was able to fly and could be spared by another squadron on the base. So, when Misty lost a plane, it wasn't necessarily from the 612th, or later the 416th.
During my tour at Tuy Hoa (Oct '69-Sep'70) Misty lost so many Fs that 5 more were ferried in from the training base in Arizona. I also have seen photos of early Misty pilots standing in front of an F at Phu Cat, but the F was from a squadron at Tuy Hoa with SS tail codes - "on loan" to Misty. As a matter of Fact, Bud Day's plane - the Misty F-100F with his name on the side- was from the 309th TFS at Tuy Hoa with SS-951 on the tail.
All that leads to the point that the tail code on 954 when it was shot down needs to be determined by another source. I don't know what source that would be, but I can try to find out via F-100 friends.
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Joe Vincent
IPMS*Memphis