I remember back in the seventies buying George Iv pennies just the common dates mind at 50p to a £1 same with halfpennies - I think you would really struggle to get your money back even now on then - stitched up is the word , I think most dealers sold modern (under 40 years old) to suckers at vast profits.
Only now do we now understand how common some off these coins are mainly to do with ebay provideing a level playing field.
Another thought back then we never really understood just how common 1839 and 1853 farthings are as well , I would suspect that many a collector in the seventies would have known they were common , but not how common.