I have to put more pressure on mine than I expect to get it down. There is no pin or anything holding it up, but it is a rather stout spring that you need to overcome.
I bought one of mine from a lady that had it for over 30 years, and boy did her eyes get big when i popped open the right side to get a good look at the treadle wheel. She considered it a wonderful display item that came with the house her then boyfriend (now DH) had bought. She never messed with it, it still had all the original "neat stuff" in the drawers.