A bit like all those fake round £1 coins that flooded the market before the 12-sided bi-metal ones were designed to combat forgery. Apparently 3% of pound coins in circulation were estimated to be forgeries at one point.
Thanks. Your latest pictures are much better, and I'd say your coin is not a problem - it's struck slightly off centre, but that's not unusual for early milled.
I agree - it looks kosher so probably a misdiagnosed denomination. But I'd say $150 is still B bit on the steep side for the most common 2/6 in the series.
You'll need to check with proper collectorists but l'd guess the Four Pence could be Maundy Money.
All your coins are beautiful compared to the filth l have! I'm more interested in the metal than the coin.
Oh and silver is worth a bit more now so revise any value estimates upward. I use eBay as a gauge of attainable value but l've recently realised low-priced fakes might be artificially lowering the bar and in any case your coin quality should command a premium.