Question about sharpening old-school tin snips

[Kozzy]

Although one could muddle through and probably get it right, I was wondering if anyone had seen information in a vintage book or other source regarding sharpening old-school tin snips.  None of my old references seem to make mention of it and I was curious if there were specific tips, tricks or other info to get the old ones sharpened "right".

I'm trying to bring a few old ones back into use for some tin-work demonstrations at the museum---and I'd not only like them to work as well as new (and this style never worked great in my experience) but be able to give reasonably accurate advice if a museum guest asks about fixing up the old pair Grandpa left him.

Thanks for any help you can give or pointing me to any information source.  I can fake it but it'd be nice to see what PEXTO or others recommended for sharpening procedures 100 years ago.

Stole this photo from the internet as a reference.  My pile is at home without pictures.

[BIGGUNDOCTOR]

I just dust the top bevel with either a file or a stone at the original angle. You do not want to hit the side, just the tops of the blade.

[ThomasPowers]

Like BGD I restore a straight flat bevel using file or stone and then if extensive work had to be done I will give the inside flats one pass with a stone to remove any wire edge that might be folded over.

I really like the bulldog snips for cutting bandsaw blades and pallet strapping---the ones marked "for alloy steel" (and always cut from the back of the blade and let the last hardened bit snap off...)

[stevomiller]

If the edge is dented or flattened, I will first burnish the inside flat to try and move most of the displaced metal back where it belongs. I then do just as the gentlemen stated above. On the edge proper I often blacken just the edge bevel with a Sharpie marker so that I can see where I’m abrading.