From 1748 to 1767 all officers except midshipmen had two orders of dress, full dress and undress, the former being much more elaborately laced. With successive regulations after 1767 the full dress uniforms were dropped leaving the undress as the only order of dress.
This is one of seven Royal Navy officer templates of the first 1748-1767 pattern, which were commissioned by Paul who runs the St George's Squadron of the Pirates of the Burning Sea online game: see here: http://www.st-george-squadron.com/sgs/wiki/index.php?title=1748_Pattern and here: http://www.burningsea.com/page/home He has kindly agreed to my posting them on the blog.