I'm the verified absolute worst at distinguishing suit jackets from sportcoats, but I wouldn't be so quick to assume that it's an orphan just based on the fact that there's a drop. Many brands (Canali, Corneliani, others included) will list a drop even with sportcoats/when there aren't corresponding pants. Regardless, it's definitely a rockable pattern without pants. Great jacket IMO.
Thanks for the info. No listed size and I'm terrible at eyeballing overcoats. Think I'll bring my tape measure when I head back for the Hawkes tomorrow. If anyone is interested in the overcoat PM me your measurements and we can play proxy roulette