Vintage caliber 321 in "Silver"/Steel finish

Hi OF,

During my usual browsing of vintage Speedmasters for sale, I saw something unusual - 145.012-67 with caliber 321 with a Silver-color finish (I don't know if it's just steel or any kind of plating).
The seller's story is that it was plated "with some metal" many years ago by Omega enthusiast who wanted to "mod" his watch by "silver" plating the movement and installing a see-through case back.

The whole watch is rather fishy (missing the original case back, heavily polished case, and replacement glass) so I don't really believe that story. But I'm curious what really happened there? Is it possible that it's Lemania movement with some modded elements from Omega 321? or maybe it was a possible way to "renovate" the rusted movement?

I am not an expert but I think is just steel and a lot of polish job..

Thanks all! Indeed, looking now at the texture (decoration) it looks like it's plated as the lines are not as deep as they normally should be.
By the overall condition, I still think that it was done out of desperation to restore the movement, other than to mod the look, but probably the reasoning behind that is not that important

I am aware of a handful of collectors who 'mod' their vintage pieces with different dials, hands, and see-through casebacks (while preserving the original parts), but to re-plate a movement does sound a bit fishy. From the picture it doesn't look like a terrible job but then again I have no experience in metalworking and plating 😁