One of my rationales in my shipboard uniform description was DGP's
World Builder's Guide and the TL 14 IISS Duty Vacc Suit. Seems to me that it was too good an idea for the IN not to have it too. There is also the illustration on the cover of
GT: Starships, for that matter.
I also took a page from an illustration of the dress uniform of the 1914 Kaiserliche Kriegmarine (Imperial German Navy). I did, however, draw the line at sailor bibs and hats with ribbon tassels on them. Imperial Navy Spacehands do not look like Popeye. I'll leave bosun's whistles to the individual GM.
As to the shirtsleeve order, I just kept with the theme. The 'basic black and gold' seems to me to be a practical theme.
Insofar as rank is concerned, the illustration on page 69 of
Traveller: 1248, Bearers of the Flame showing the bloody sleeve of a flight branch commander over a reader display was my primary guide. Also, I kept the
Traveller's Digest article that describes the Imperial Joint Services Rank Insignia in mind (colored Sunbursts indicating rank). This insignia is worn on a magstrip from the right chest pocket in those areas where they are required by regulation. As to the black and gold belts, I have several friends in the USN Submarine service and they explained that at sea you could always tell an officer from behind by the khaki belt they wear, it being different from the navy blue belt of enlisted grades. Like the shipsuit, it seems to me to be too practical for the IN not to adopt.
Other than the insignia of the various Knighthoods in the full dress uniform, there is no special insignia for nobles. Relative wealth is displayed in the quality of uniforms and adornments. This is in keeping with British Royal Navy tradition that whatever his breeding, an officer of HRM's Navy should be an officer first and foremost. HOWever, we have the MT canon statement that nobles are required to carry a highly decorated magnum revolver in the presence of the Emperor. I don't think it would not be too far a flight of fancy to see Sblt. The Honorable Eneri Stanford-Giirki, Baron Yasoub, carrying his magnum revolver in place of the IN issue gauss pistol on those occasions where wearing a sidearm was appropriate. You must admit, it would smooth things with the eldest son of the Aslan
ko his Captain is negotiating with to have an easily identifiable fellow warrior-noble to talk to.