Does this British 1745 LIMA Half Crown Look Authentic?

[Halfcrowned]

I'm fairly new to coins, and the only reason I ask is because the size of this in hand is a bit bigger than my other half crowns of the period, which all seem to be around 32-33mm. It seems to sit at around 34-34.5mm. It weighs 15/16grams on my (cheap!) kitchen scales, is non magnetic, and has the correct side inscription - DECVS ET TVTAMEN ANNO REGNI DECIMO NONO.