At this time TSGT Nelson was a regular on the Dahl Crew. He flew some missions with other Lead Pilots like Brownlow, Parks and Kittel. But at the time this photo was taken, he was with Dahl. This was on 42-29890 Madame Pisonya a.k.a. "Stupefier" FR-E and as you can see LF-J was her RCL.

The date for this photo is 31st August 1943. The crew had returned from an aborted mission.

Back row L to R. 1st Lt Arvid O Dahl, Pilot. 2nd Lt Weldon N Bledsoe, Co-Pilot. 2nd Lt Constanse Anszperger, Navigator. 2nd Lt Thomas J Macmorran, Bombardier. T Sgt John B McCullen, Top Turret.

Front Row L to R. S/Sgt Patrick F Romano, Tail Gun. S/Sgt Edgar M Taylor, Waist gun. T/Sgt Marshall L Fisher, Ball Turret. Sgt Robert Pickle, Waist Gun. Sgt Ole K Nelson, Radio.

Source: American Air Museum: https://www.americanairmuseum.com/person/35861