Scottish (Mary?) 1 pluck

Hello!

I'd be grateful if someone knowledgeable in Scottish medieval coins can positively identify this one:

copper(?), 21-22mm, 1g, very thin

It is a Scottish 1 Plack Mary I.

Here is the Numista Link.

N#90185

My thought at first as well, but the weight is off. 

Which is normal, since the coin has been clipped a lot.

Sjoelund

Which is normal, since the coin has been clipped a lot.

Why on earth should someone do that with a copper coin?

OK, Cu is cheaper than Ag, but if you have enough clippings, it's still valuable?

Also the coin is almost 500 years old so it likely has wear and may not weigh what it used to.