This Disson keyhole(?) saw says Disson & sons , Phia. ,USA on blade.
any idea on date?
Date? Old. Strictly speaking, this is a pad saw, since the blade slides in and out of the pad or handle. I don't know an end date for production, but it is illustrated in the 1876 Centennial catalog, which describes it as:
"This is a cheap and convenient combination of a Key-hole Saw, Saw Pad, and Screwdriver."
The ad man got a little over enthusiastic. The blade shown is an ordinary pad saw blade. The only way to use this as a screwdriver is to let the end of the blade extend out the back of the pad just as can be done with any pad saw (as long as you take a file and make the end of the blade flat...).
The illustration in the 1876 catalog shows a thumb screw holding the blade in place. A 1918 illustration shows it with a hex head bolt as found on yours.