Mark Is and IIs are some of the worst most useless knives I know of, with a terrible and slippery handle.
Of course I own some in the collection because they're very cool, beautiful, and have a history behind them, but I wouldnt choose one overy almost anything else.
As for that Mark I, I'd say go for it if you're a collector or if the handle is different than the original Mark I (I know this one is full tang, I'm talking about the handle shape and length), because, at least for me, the shape and length (or lack thereof) is truly terrible and even dangerous if you're ever slashing or stabbing with it, as it slides off the hand.
I also doubt it has a sharp edge or that it can be sharpened correctly, but that's up to your skill. I also think it is too heavy to be a literal boot knife and even for a backup knife.
Here are my suggestions of alternatives:
-Fällkniven G1 (severely underrated and awesome knife.PERFECT knife for a boot)
-Gryphon M107 (Terzuola design, need I say more?)
-Katz Avenger (One of the best designs I've ever seen. No serrations available)
-Gerber Guardian (Cheap and much more functional)
-Cold Steel Counter Tac I (Ground on just one side, designed for stabbing)
-Spartan Breed Fighter (on the limit of size, it is more of a vest knife)
-Dynamis Alliance knife (A Daniel Winkler knife, expensive as hell though)