This is my first post and I like to share a coin I bought. CGS AU78 1923 Specimen (Ex The Soho Collection, London Coins Auction A175, December 2021, Lot 2104 and London Coins Auction A126, September 2009, Lot 1272). The coin has reddish brown toning with a nice luster on both sides. Field is smooth and with a few tiny marks or nicks. There is light cabinet wear on the reverse. London Coins commented that "the rims although equal in height to the currency coin are more raised from the fields".
As I am new to British copper coinage, I am interested in learning. I am not sure how to spot a Specimen coin from a normal MS Coin of this period. From what I can see on hand the biggest differences compared to circulation coins are the device and luster. The device is sharper (especially king's bust) while more grainy in appearance. Lusters are only present close to the rim compared to the whole field on circulation coins.