In your amazing map of this level, I found the four locations where the hidden switches were located. One of them appeared to be accessible only with a warp potion. I believe these were the four I found. I still don't understand why I couldn't get the silver key. I have to go back there anyway because I never finished that level; I got impatient because in level 9, I couldn't get the little guy to stay on the steps leading up to the first jewel and continous fire potion.
Your work on these classics is so remarkable. I'll be referring to these maps in the future. The mazes are annoying but an ingenious device that makes the classics more interesting. Platformers made today are really dull in comparison.
(Later) Finished the level with the map in my memory bank. I can't remember if I uncovered a switch I had missed before and never returned to the wizard, but somehow, as I was walking along, the silver key appeared in my inventory. I went on to level 9, beat the trees and finished part 2. Those trees are the toughest boss level in the game; I don't know why they didn't save them for last. Thanks again for the link to the maps; I need to visit your game site more often.