difference between medeco& average 5 pin tumbler lock?

no and yes.. more than 5, but special pins, and added security feature REQUIRING the use of the 'right' key blank as well. there are a lot of Medeco blanks, and given a series, all will go in the lock, but only certain ones will work, assuming the right pin cuts are done to the blank.

--Shiva--

Details are on Medeco's website, if you do a bit of digging.

Medeco locks' pins must be lifted AND rotated. Their spacing may be offset forward and backward ("biaxial"). And their latest design adds yet another complication.

A real high-security cylinder remains high-security even after you understand it. It isn't just weird, it's usefully weird.

In a Medeco the pins are inline and there is a shearline like in a conventional pin tumbler. However Medeco locks also have a sidebar which prevents the plug from turning even with the pins all at shear. In order for the sidebar to retract the pins must be properly rotated, as well as raised, so that notches in the pins line up with pegs on the sidebar. Further the sidebar prevents binding the pins by tensioning the sidebar so picking is very difficult. There are also inserts to prevent simple drilling.