According to Saul Teichman, there are only two examples, possibly three, of Judd 108. However, PCGS records four examples (three PR64s and one PR62) in their Population Report, so there is an error somewhere. We examined the grading events at PCGS and it is highly likely that two of the PR64s were resubmissions, but they were certified too long ago and there is no other evidence to justify their suppression. Likewise, the NGC PR62 and the PCGS PR62 are quite possibl the same coin.
This is the same die combination that produced the unique Copper 1839 $1 Judd 109.