I'm afraid that I didn't spot it. I picked up the attribution from a shilling collector on Facebook. I managed to win one 'want,' and then noticed that the 1671 plumes shilling wasn't bid on, so I snaffled it just in time. Later on, I found a couple of other varieties of Victorian shillings were not bid on, so I got those for well under the expected price. All round, I'm pretty pleased.