Could possibly be a stock number for a used part.
Wrecking yards need to be able to show proof that parts have been legally obtained, particularly for major components. IE Engine, Gearbox, Diff, and some major panels.
Typically when a vehicle was be purchased, it was allocated a stock number which was written on major, and fast moving components. Engine, Bonnet, Headlamps, etc etc.
I could be way off base, it just looks like that engine is sitting over a grate of some form and therefore out of the vehicle