All About Pocket Knives

I have some questions on a new one I picked up. I received this one in the mail last week, and would like to impose upon Dale's or Steve's (ar anybody else) prodigious brain cells with some questions.

It is 3 5/8" closed. Rosewood handles I think. You can still see the etch....has half stops, and you can hear the snap about 3 blocks away. Man, I love this knife.

1. I am guessing this one is circa 1920-1940 ?? that is a SWAG - I am just basing on the looks. Is that in the ballpark?
2. Who might have made this one?
3. Any idea what the writing on the back of the blade - looks like a plus sign (+)...or maybe an "F" / 75 ?

The handles are Cocobolo wood, the writing on the back of the blade is salesman`s cutlery ink. These were the model numbers and the cost per 1/2 doz. or each.

Thanks Dimitri! Any idea who made this one for Shapleigh? Schrade, maybe?

I would say Empire

Great Knife Unk! I have a 2-blade jack that's marked Norvell-Shapleigh with the DE logo. My book says 1902-1917 on it. Not sure who built it either. Same book states Walden Knife Co., Schrade, Camillus and others. They are excellent knives. Congrats! WB