pvtcook said:
Digger kind of what I thought but when you pay a grand for one what's a extra $20 lol.
Coil covers came about in the early days, the coil of wire was sealed between to plastic shells, many called these "Box Coils" and they were hollow so it was possible to crack, or wear through the bottom of the coil. To solve the problem coil covers came to be, wear out a cover, just replace it.
Things have change in most manufacturing of search coils, the more modern coils only use the upper halve of the shell and the lay the wire windings in the upper most part of that and hot glue them in place. While its still upside down they resin fill it. In this design there isn't a plastic shell for a bottom to wear through, but rather over a 1/4" thickness of resin. So, the upper halve of the shell is also a mold.
Now, some still buy the coil covers because its something they have always done,
Others buy the cover to just help keep the coil in a less used looking condition, it does help on the resale of the detector for it to be in as pristine condition as possible.
Some buy the covers because they believe that it protects the bottom edges of the upper shell from getting cracked or chipped off.
Whatever the reason is for people to buy them I'm sure the sales are helping to support the manufacture's and that's a good thing!
Some have gotten creative by removing the cover, taping the outer edges of the upper shell and covering the bottom's of the coils with that spray-on truck bed liner. These protects the bottom surface of the coil, gets rid of the need to remove and clean the coil covers.
The picture below is a detector manufacture worker pouring in the resin on a assembly line for their coils. (Not First Texas Products)
Mark