He is a total rivet counter when it comes to old airplanes.
rivet counter
idiomA person who has an obsession with the minutiae of their particular interest, especially in military and technology history. Anyone preoccupied with small distinguishing features between different items.
The online forum was full of rivet counters arguing about the exact shade of paint used on the tank.
While the casual historian enjoyed the documentary, the rivet counters spent the entire evening pointing out minor inaccuracies in the equipment shown on screen.