Strange screw heads

[jolly roger]

Hi David,
              It's a Robertson head, Canadian Invention, Great srews, the
driver rarely slips off, and the don't need a self grip driver to use in
hard to reach places.
If you are really stuck, I could send you some at what ever it cost.
Roger


At 06:50 PM 7/28/01 +0100, you wrote:
>Hi folks,
>
>I wonder if anyone (in the UK?) has come across action screws like these? 
>I tuned for a new customer yesterday, an old straight-strung upright, circa
>1920, pretty standard cheap quality English upright.  I took the action
>out, and noticed that the flange screws had odd heads.  
>I pride myself on having every kind of screwdriver - flat, Philips, Torx,
>Hex, Pozidrive, Security Torx etc.  These screws, however, had heads with
>SQUARE holes.  Looked like Hex heads at first, but square.  A new one on
>me!
>
>Best regards,
>
>David.
>
>P.S. I got one out using just an ordinary flat screwdriver placed
>diagonally in the hole.
>