All I've been able to find on "coin mail" is this

http://www.rpgworlds.org/glossary/armor/coinmail.html

Is there any evidence that coin mail ever really existed? Surviving examples, or written records? It'd also be interesting if anyone had any pictures of coin mail that are authentic if they were ever any to begin with. Considering that my source for it in the first place is from an rpg site I doubt there was ever such a thing.

Aside from that I've seen several people nowadays make makeshift scale armor by using pennies and nickels instead of scales.

"Mail" is defined as a series of rings interlinked so as to form a mesh. No other type of armour can be called "mail". The armour in question is sometimes called "bezainted" armour where coins or metal discs were used to reinforce cloth or leather armour. If the coins overlap enough then it might be classed as a type of scale armour. In Medieval Europe there was a type of armour called a "pennyplate coat" though I can't think of any surviving examples. Stone's Gloassary has a photo of Alaskan (Sitka) leather armour reinforced with modern Chinese and Japanese coins (p.22).

From the description, it sounds like a rich man's version of the penny plate coat. The penny plate coat, which was made with discs of metal or even horn, was effective as armour as part of a protective system.

The description in the link you posted appears to have been ripped out of a Dungeons and Dragons "Arms and Equipment Guide" from the early 1990s. I'd have doubts about gleaning any useful information about arms and armour from such a resource.

The Roman Lorica squamata is a scale armour, but the scales are not round. The top is square, bottom is rounded. The scales were joined by small rings and sewn to a leather undergarment in rows, much like roofing. I suppose the pennyplate "mail" would be made in much a similar fashion. Perhaps someone has a picture of one or more of these disks preserved ??
There is discussion on whether or not the scales have also been added to mail as an outer layer, somewhat like the breastplates over mail. This would be very heavy, indeed, my mid Roman 6 mm riveted mail (by DSC) weighs about 12 kilo's, scales would certainly add a good few kilo's to that.

I added a link of a Roman re-enactment group which has both a good descripion as well as an interesting picture of interlocking scale armour : http://www.legionsix.org/body_armor.htm