I am intrigued. I will attempt to reserve comment until I see an example of this coin insert...but I am going to fail.
WHY would anyone want to fill the bow divot with an ornamental coin? The divot is one of the reasons I bought the 5! Similarly I have seen people fill their Spyder holes on Spyderco knives with coins...I just do not get it.
In the end, it is not my knife, so who cares what I think? Do whatever you like to enhance your enjoyment of the knife. Personally, if it were up to me, I would get a coin that has some significance to me and measure it, then mill out another shallower hole in the micarta to receive it. Enjoy your mojo, and your divot...and your mojo need not be limited to a single size.