Current standard 149s are delivered with an 18-carat gold nib, while older variants of the 1990s often had 14-carat nibs, which explains the discrepancy between an older personal piece and newer special editions. The change to 18 carats took place in the early 2000s as a general upgrade in model maintenance. In France 18 carats was already common before, because there gold is only spoken of from this purity, which is why country-specific nib variants existed in the past as well. The 149s auctioned for Unicef as well as the three limited Unicef-4810-149s (e.g. Tom Sachs) carry 18-carat nibs, which underscores the special significance of the literacy project.