Interesting notes from my father!

According to him it is a court coat, unusual to see with a kilt. It is probably (assuming it's not just a one-off show piece or experiment) diplomatic in nature, hence the presence of a military style gauntlet but no epaulettes.

In all honesty it would be quite an expensive endeavour. Normally for this type of thing I would refer a customer to a military tailor, the absolute best person for the job for a commission like this would without a doubt be either Davide Taub (Gieves & Hawkes) or perhaps one of the naval chaps at Dege & Skinner, but you're probably looking at several thousand dollars, plus obviously a visit to Savile Row!