1991 is the year the Libertad expanded beyond its original 1 oz-only format, introducing fractional sizes (1/2, 1/4, 1/10, and 1/20 oz) nine years after launch — the first step toward the unusually wide size range the series is known for today, which later grew further with large-format sizes added in 1996.
A 1991 Libertad could be any of five sizes, unlike earlier years which are 1 oz only — confirm the specific size on any 1991 listing, since this is the first year that ambiguity becomes possible.
Log the year, your cost basis, and photos — and see it valued at today's spot price alongside the rest of your collection.
Start tracking free1/2 oz, 1/4 oz, 1/10 oz, and 1/20 oz, alongside the original 1 oz coin — the Libertad's first expansion beyond a single size.
Not for scarcity specifically — it's notable as the fractional-size introduction year, similar to how 1980 works for the Krugerrand.