Well now you know some more...
What about dates? There is hardly any information regarding dates on razors - they don't have the date they were made stamped in them. Even when you have a name, the person after whom the firm was named could have been dead for donkeys years, so the name wouldn't tell you much.
As for Erustas, it seems that the majority (based on an image search on Google) do not have the tack-type pins. As for dating them - well, there is hardly any information available on the company other than they used steel from the Bohler Steel Company, so the best you can do is use a gut feeling, which isn't very helpful. I have seen Erustas that could possibly span 1930s to 1950s, but I don't know - I bet your mate doesn't either.
Attachment 173759
Attachment 173760
Attachment 173761
Attachment 173762
The above look somewhere around 1950s to me. That would have the partial backing of Bohler Steel, who diversified in specialist alloys in the 1950s in a big way.
And they don't have 'those' pins...
Attachment 173763
Attachment 173764
The first pic shows a pin set, complete with the hideously thick (IMO, of course) friction washers. You can clearly see the pin is a small tack or nail.
The second picture shows the nail head - the small circle in the centre equates to the diameter of the pin and the head is formed so as to resemble a washer, but is obviously not. Very clearly these are not used in either of the Erustas pictured above.
The end with the cupped-washer looks decent enough, so it is surprising that the modern trend seems to be to put it at the back of the razor and leave the ugly abortion pin-head (IMO, naturally) showing on the front.
I have used them but they are best used (IMO yet again - gets tedious, doesn't it) with the nail head cut off and another cupped washer used instead.
Regards,
Neil