here's a littletutorial
the ideais mainly toretrievean oldzoomwhichwas uselessbecauseof poor quality.
abottlecap(I usedonesimilar to thatof the photo)
a lensonaZoomrecoveredorpurchasedat electronics stores
you have to disassemble the the "objective" (the poor one are easy), then retrieve the wanted lens
to know if the lenswilldo the trick,make the testas in the photo
therest ishistory,the photosspeak for themselves