I believe this extremely rare model is a built kit. It is an estate sale find. The paint job is fantastic and so are the details. Upon assembly the wheels seem to be a bit off centered - see pics. Below is a description I found in a recently sold listing for the same model.

"This Trinity Models Ferrari 312B3 in 1:24 scale is a rare find for any Formula 1 car collector. The attention to detail on this die-cast model is impressive, capturing the essence of Niki Lauda's iconic car driven in the epic 1976 Formula One season.

Trinity Models was formed by Peter Hancock who had been a model builder for Lamberts of Ley St - (a specialist model shop in England which closed many years ago). Peter formed Trinity Models and got contracts to build models for some of the race teams. Later Rob Ybema who had been making one off models in 1/24 joined and they got various teams interested in resin built models in 1:24 with masters produced by Rob. Trinity disappeared many years ago."