Suprisingly old bean I think that these initials would make the best name for this trick as in the UK these little plastic boxes are found in Kinder Surprise Eggs, so the alternative meaning for KSM would be Kinder Surprise Magic (although you might have a couple of copywrite issues)..
I think I mensioned it in another thread, but you should check out Jay Sankey's "Magus Capsule". It has a similar shape to the egg in a Kinder egg, it may give you some ideas
It's a nice trick. Once you've worked on those moves a little more, it will be great. Could be some interesting patter for it, too. I still prefer the Kinda Suprise name. That is genius!
Just a thought- rather than having an imaginary coin, why not try it is a transposition effect? If you set up the egg and place it on the table (or even have someone hold onto it) and vanish a coin, the reappearance in the egg will be quite startling. If the coin were to be signed, and a last-minute switch was used, you could have a potential baffler. Just some ideas
Yes it's a differen't trick, but it uses the same technique. Just show the egg empty, do the 'stuff', take a coin and vanish it, only for it to appear in the egg. You see it's just adding a vanish, making it look like the coin transposed rather than just appeared. So there really is not much to develop, just do a vanish then procuce the coin.