Interesting that there was a trace of the missing bar, as it is completely missing in the examples I found on auction sites. This contrasts with the so-called xxr error in the 1881, where there is almost always a trace of the missing serif. In both cases, I think a broken punch is more likely than die fill, given that only specific letters are affected.
Also interesting that florins were being catalogued as "onc" as early as 2005-7. Does anyone know when onc florins were first spotted? All I know is that they are in the 7th edition of ESC (2020) but not in the 4th edition (1974).