I understand the physical difference between a ma*****c half and a sh****d half, but what is the differecnce in strength? Or, does it depend on the manufacturer? I would like a half with this physical property, but not shure which one is best for my application. I think I would prefer a weaker one for holding out and such.

Is there a coin set/trick that I can purchase that has one of these plus some other coins (more bang for my buck)?

These two coin gaffs don't simply have varying amounts of some particular physical property. The magnetic one has a magnet inside and is, well, magnetic. The shimmed one has a steel core and isn't magnetic at all. If you want one that sticks to steel, get the magnetic one. If you want one that will be attracted to a magnet, get the shimmed one.

Of course a magnetic coin will also be attracted to a magnet, so polarity and strength might be concerns if you intend to use such a combination.

One or the other of these gaffs might come as components of other effects such as Johnson's Visible Coin Penetration or various gimmicked Okito Coin Boxes, but at only about $18 for the steel core and $25 for the magnetic (in Johnson's, a bit less for lower quality), it might be most efficient to just purchase the one(s) you need.

Greg

Onebark,
Are you specifically looking for a half, or just looking for something with these properties to play with? Hopefully I'm not too far off subject in recommending a Johnson magnetic copper/silver set. You get a four piece set, several cool ideas, and many, many possibilities at a pretty great price.