Help needed

Jim Jobe took this photo at Middleton St. George in 1961.
MANY THANKS to Jim !. The photo is Copyrighted © by Jim. It shows 3 aircraft carrying the serial numbers XN459 / 20 , XN506 / 31 & XN510 / 36.
All these aircraft were based with 1 FTS at Linton in 1961. However none of the "GIN Section" pilots from that year have an entry for Middleton St. George in their log boks for that year & none of them remember flying an aircraft with smoke tanks attached to the wings.

Can anyone out there, provide more Info / Clues ?

Click on Jim's photo for a higher resolution version.