Gonna take a wild eyes guess ... N10607 44-74466. Dick is sure a master at providing almost "no hint" photos.
So far, Roger is the only brave soul to take a stab ...
HINT: Dick has not left much to go by on this shot. So I'm going to give you all a small hint. This P-51 is no longer around and it is not in the MM survivors list...
This photo would most likely between 1963 and 1966 because this P-51 served in 4 different air forces and took a little break stateside before taking a last ride across the border... ... the records I have show the N number switched...
3 Mustangs at least would fit the description: 44-72291, RSwAF 26055, FAN as GN-83, MACO N614OU, FAB-512. 44-72059, RSwAF 26142, FAN as GN-??, MACO N615OU, FAB-513. 44-72031, RSwAF 26021, FAN as GN-??, MACO N6152U, FAB-514. According to Dan Hagedorn and John Dienst, the 2 last Mustangs were operated by the FAN between 1955 and 1963, were purchased by MACO in September 1963, went to Aviacion Sanford in 1966 and onward to FAB in June 1966. The first one might have had the same history as it also went to FAB in June 1966. Now 44-72059 is on your survivors list as being restored at Vintage Aero. That would leave 44-72031 or 44-72291.
Marc: You are gettin very warm!
I've had a look at 2 websites listing RSwAF J-26s :
These sites agree on the fact that Fv 26021 aka 44-72031 aka FAB-514 was N6152U.
44-72059 is listed as N6150U, not N615OU.
According to the second site (.../kionga/J26), this plane is the Mustang previously displayed at the FAV museum in Caracas and is now with Vintage Aero in Maine as N951HB. This is interesting because I've always seen the Caracas Mustang (your P-51Who case#179) identified as 45-11458, FAB-504. Is it FAB-513 ? Has the Caracas Mustang found its way back to the States ?
On both websites, 44-72291, aka Fv 26055 aka FAB-512, is identified as N6149U, not N614OU or N6140U. Is this the switch in N number ? Also interesting is the fact that the second website (.../kionga/J26.) reports N6149U as crashed at Springfield, IL !
Anyway, my best guess for Case#210 is 44-72291, RSwAF Fv 26055, FAN (GN-83?), N614?U, FAB-512.
Certainly this is an ex Nicaraguan F-51, and is photographed in a line of several Mustangs. The aircraft parked to its right was N6163U, GN90, and I can see this one in the background of a contemporary photo. With little else to go on, I can guess it is a shot of 44-72291 ex RSwAF 26055, FAN 83, and becoming FAB 512 in June of 1966. There her trail grows cold....
Regarding P-51D FAB 512, my logbook shows that I flew test flights in that '51' for MUSTANGS UNLIMITED @ ATL on June 4th 1966. FAB 514 was there at same time being prepped for the trip "south".