The way I understand the nomenclature, technically, a reverse proof should have fields that are frosted (or matte) and devices (raised areas) that are polished....which is the opposite of what has typically been considered a proof finish (fields polished, devices frosted or matte).
The collector version of the kilo Libertad is basically a very large reverse proof coin. As db23 noted, the Banco de Mexico is who has initially decided to label their reverse proof kilo Libertad a "Proof-Like" Libertad....bucking convention.
The 2015 1 oz reverse proof Lib is NOT the first reverse proof Lib...the first year "Proof-Like" kilo Lib (2002) is....so APMEX has it wrong.
The lowest mintage reverse proof Libertad is the 2013 and 2014 "PL" kilo Libertads with only 400 made in those 2 respective years.
https://en.wikipedia.org/wiki/Libertad_(coin)
Incidentally, it looks like on eBay and some other dealers websites, prices on many of the "PL" kilo Libertads has been inching up lately.
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