These are stamped "Perfection Shear Co." and "J?n 1910" but neither of those gets good search results. The scissors seem to be a copy of Keen Kutter style buttonhole scissors. The knob is free and comes off the screw post completely and does not affect anything right now.
A flat spring holds the pawl in place. I have got some of the dirt out with a toothpick and I can get a thin screwdriver between the spring and the pawl. It is the side where the pawl is against the scissor handle that is stuck. I cannot get paper or a fingernail or a straight pin or the thinnest screwdriver in there. There is space behind the hinged end and the 'backside' of the handle, but no space between the free moving end and the 'backside'.
This is what the pawl is supposed to look like when it is free to move.
The same picture as the link above but you can zoom in on it here.