In the first part of this series of notes, the lead alloy counterfeit round pound coins were introduced. In this note some of the more unusual counterfeits will be described. Ranging from resin coated lead cores to impossible dates to an overstrike on a foreign coin, the pieces demonstrate the ingenuity and skill of the counterfeiters. Though the coins were circulating only a few years ago, all of the pieces presented here are now very rare.
Counterfeit Round Pound Coins (ii) Unusual Issues – G. Oddie
BNS Research Blog 
For correctness, the counterfeit shown in figure 8 of this article “overstruck on a Turkish 10 Bin Lira of 1997” belongs to Paul Baker. The image had been given to EN, but the attribution lost when forwarded. My apologies for the error.