I  submitted a post with answers on what knife is what but decided to give answers tothe clues.  Answers in Bold.

Clue #1:

The middle knife only has one blade.  Easy!

Clue #2:

At least two of the knives are from the same maker.  Yes. They are.  Oh...the top & the bottom are Shrade.  But top i Walden, N.Y. and bottom is CUT Co/Walden N.Y.

Clue #3

At least one knife has celluloid grips.  The Frot, tho all three look and feel like celluloid.

Clue #4:

At least one knife has markings on a grip.  The Schrades are both marked "Office Knife".

This was so much fun I wanna do it again.  Anyone interested???