And you would be correct. 
Along with “virga” from the thread on biz jets, I’ve learnt two new words today
Unfortunately this means I have lost two other facts to make room, so now I have no idea what to call a more than half visible, but less than fully illuminated moon, or how to make chutney
Meh, nothing so fanciful as what’s been posted (well, except the comment about them using lots of razor blades and just putting them down or hiding them.) The one nailed to the wall with “7-78” written above it is probably the reminder blade. When they need to go get replacements, they go look and confirm the blades they need are 7-78 blades. Could have just as easily been an old package nailed to the wall, but this was probably handier for them.
As far as the blades lying around all over, it’s probably the same reason if you ever went to any of the grocery stores I worked at during HS or college you’d find razor blades in strange places; they had to swap blades in the middle of something, and just sat the old one down on the first handy surface, forgetting about it moments later. OSHA rules or no, if I went back into any of those places I had worked, I wouldn’t touch any flat, horizontal surfaces without first checking them for old rusty blades left there for years and years.
“My brain is full. May I go home now?” more or less quoted from Gary Larson