1991 Penny Double D Error Worth?

To CFF!
I've personally found a few of these coins myself, and it turns out that usually they are not DDO's but either split plate doubling or just the copper running away from the zinc. On the 1991 D DDO, Liberty is also doubled, and in the other picture I can see no doubling. Fairly common find, but if you saw this you have a good eye! Keep collecting!

LMCs after 1982 (transition year from copper to zinc/copper plate) and LSCs are susceptible to hydrozincite (typically referred here as zinc rot). The copper layer is very thin and stretches even thinner at various points on the cent, especially in areas where the blend radiuses between the devices and the fields are sharp (e.g. around the mint mark and motto letters). This is even more the case on 1982-1989 LMCs where the mint marks were still hand placed/stamped on the dies. The sharp blend radiuses on these coins result in many cents catching the rot and disintegrating. 1990 and later specimens have the MM as part of the engraving and the radiuses on these are softer and less likely to be the focal point for rot. Finding AU or better zinc LMCs/LSCs that will survive intact over time is a challenge. When CRHing, I look for MS grade specimens with the hopes that at least a few will survive the next 30-50 years. For instance, finding a 1984D LMC in AU+ condition is very difficult.

PS - Jon to the mix here at CCF!