When you replied to my post on the stub tailed razors I immediately thought you were the one who outbidded me on this piece!
Obviously mine is the other one from the same seller...

On this page From Perret to Kampfe: Origins of the Safety Razor you can see a picture of Perret's invention of his safety razor (and the way to handle it) taken from his book "La Pogonotomie": the shape of his blade strictly reminds me to the ones we have, and the book is dated 1769.

This doesn't mean that our blades are original (although mine is so thin at the tang that I don't think it could have had a tail) but, should they prove so, this can maybe give an idea of their period.
So now we have two similar razors (this and the WWI, right?): please don't tell me you also crave for John Barber!

Cheers,
Mauri