NGC means "Matte" Proof for the 1931 Proof coin in the table below, right? Otherwise, that'd be a sharp looking but poor surface example of that Panama Balboa type! I think they need someone full time to edit and revamp the world coin guide, namely with better pictures or adding pictures that are absent altogether. Too bad NGC hasn't really been responsive to emails regarding site errors lately, at least recently for me. https://www.ngccoin.com/price-guide/world/panama-balboa-km-13-1931-1947-cuid-6249-duid-22236
NGC has basically uploaded the Krause catalogs to their site. You'll notice that the pictures, information, numbering, and valuation is all based on Krause. So, someone really needs to re-vamp Krause. And that is a complaint that has been made for a number of years.
I'm not going to pretend to understand what they mean by "proof". Basically, we need input from another source other than Krause. There must be another resource. I've found this so far from a Spanish-language coin forum site: País: Panama Año: 1931 Valor: 1 Balboa Ceca: San Francisco (California) Material: Plata 0.900 Peso: 26,73 gr Medida: 38 mm Tirada: 200.000 Canto: Estriado Grabadores: Sr. Roberto Lewis ( anverso) & Sr. William Clark Noble (reverso) Km: KM# 13
