Great Britain 1927 Crown Proof?

Good news and bad news.
Good news:
All of the 1927 dated British Wreath Crowns are proofs.
!5,030 of them were struck.
Other later dates of this type were struck in 'uncirculated' quality as well as proof, but in much smaller numbers, in the range of 900-9,000.
Bad news: This example has very slight wear, somewhat obscured by the rich patina, so it is an impaired proof, and so is probably valued at perhaps only 70% of the value of a perfect example.

Nevertheless, still a very nice coin to have.

It must be remembered that proof coins struck before about 1960 did not have mirror fields, with cameo design details, they were just struck to the best quality possible, with new dies, often at increased strike pressure, and often with multiple strikes to improve die impression into the coin.
Modern mirror cameo proofs are made differently to satisfy the preferences of modern collectors.

Beware of top quality fakes of these. Genuine coins are very scarce, and so attract the attention of the Chinese fakers.
From my very limited skill in declaring authenticity with this series, I believe this one is genuine.