That honing guide is a venerable old thing, very nice to have it bundled with the plane!
It is a very simple device so it could be missing nothing but look like it is, as far as I know
this is a complete one for comparison on the Old Hand Tools site. I should probably add that a certain well known/infamous US site that sells old tools has one listed for nearly 200 bucks and calls it "very rare", but I don't think that's at all accurate or realistic!
Now whether you should make use of it is another thing. Sharpening freehand versus with a jig is as you might have seen since you joined a hot-button topic here and I'm not trying to ignite that debate because I feel anyone should use a guide if they want or need to. But this one specifically is perhaps not the easiest type to use, which may be part of the reason it was thrown in with the sale.