Just for the sake of argument, I'm leaning towards a restock.
it looks to me like the buttplate from an older, wider butted gun was crudely fit to a later, narrower stock, possibly one that was roughed out for a back action lock. One clue is that on the off side, there is a nice tapered edge on the lower portion of the buttplate, and wood was obviously removed in that location, whereas everywhere else, the plate has a sharp edge where it was cut down to fit the wood... Likewise, the top of the return was filed flat to match the top of the comb. The return was originally much wider and either rounded or facetted. The fitting and inletting of the mangled plate are obviously not best quality.
I think the guard originally went with the buttplate (and barrel/tang, triggers, and lock). The poor fit and the unneeded straight cut on the curl of the return makes me think it was originally on another stock with much less drop, where the cut might have pressed up against the trigger plate and the guard would have fit the triggers much better. Further, there appears to be a crease on the bottom strap, probably from bending? The front return is being pulled away from its inlet, also, as if the fit was forced.
The brass triangle side plate likely was an expedient replacement for a nicer iron one that probably didn't work without real panels.
The entry pipe skirt is crudely and unevenly trimmed, so if it went with the other pieces, I suspect it was bobbed.
The nosecap could have been reused, but the fit isn't perfect.
I think the original rifle was late Flint period possibly, maybe had a nice side plate and patchbox.
Just my thoughts, and open to corrections, as I'm good at missing the obvious
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