It mean Ziltch. Nada, a common way to try and "upgrade" the price.

A grade have meaning only if you can give a clear definition as other
wise what stop you from tomorrow call this UNC++ and than UNC+++ and so
on.

I believe this is as bad as grade soemthing as Average circulation and
to some degree also Gem and Choice after all if Choice is MS63 than
call it MS63 as otherwise someone might consider Choice as MS62 or MS64
etc. Gem for example used to be MS67 and now it more accepted as MS65.

What a great hobby we have.

Have fun.