Like you Tilly, when I decided to build this model, I chose to use those two photos of 93 at Vospers as the main source of detailing. They’re high resolution photos and can be enlarged usefully to give really useful detail of many of the fittings
Note that the for’d monitor is positioned much further forward than the later ones and there was no breeches connection.
Also, the lifting eyes extend down, outside the hull and the RAF roundel has no white or yellow outer ring.
Mine is a 34 inch version, based on the original Rowell design, but all scratch built, including all fittings. The main construction differences were to add tabs to the top of each of the bulkheads to allow them to be fixed to a base board during the build. This allowed extra longitudinals to be added to the front third of the hull that in turn allowed that front third to be diagonally planked to achieve the true hull form of the original. I also made the cockpit roof removable to allow access to be able to clean the fitted instrument panel at a later date.
I’ve attached some photos of it since recent completion. More details later.

I think you'll find that those photos are not of Pounds Yard, but of Vospers Yard at Portchester where the tenders were built. Indeed the pictures are of 93 having been recently built and in 'original' condition. Compare it with the photo I have attached that is of the tender undergoing sea trials with a Vosper (?) civilian crew, the long nozzle monitors, a Red Ensign (Military vessels prior to acceptance) and Flag Alpha - ship undergoing trials. The other photo is of Vospers Portchester Yard. You can see the jetty where the tender was berthed for the photos

Going back to your query RNinMunich, something over thirty years of my life was as an engineer officer in the RN. Half in sea going appointments and the other half spent mainly directing ship support and maintenance. Great times!!

I spent a bit more time today reading up about DF systems. Loop antenna on Wikipedia was interesting. it seems to me that a simple manual DF loop would be a feasible option for the teardrop; it was certainly that on many varied aircraft at that time (inc the Wellington). Also, thinking about the size of the teardrop, it may be small for a DF loop, but comparing it to the other navigation lights, it's really too small to be one of them! I love chasing all over the net trying to find positive solutions to little mysteries!

Knowing v little about radio waves and antenna construction, I'm happy to accept your line. My assessment was purely on trying to identify the teardrop's purpose and matching its shape to similar units in RAF use. it was usual for ships then - merchant and military - to have a DF system and it just seems logical for a vessel with search and rescue responsibilities to have one!

Positioning of nav lights was subject to complex rules in the 1950s and still is! One thing, that I don't think has changed, is that the for'd steaming light must be mounted a significant height above the red/greenside lights. The cabin roof would not be enough!

Interesting that we both have similar lengths of experience associated with similar naval vessels. Maybe we crossed paths sometime gone!!

Interesting, valuable photos and drawings. More like that would be welcomed by many of us.

As it would have been illegal not to have a stern light on vessels like these, for both normal passage and also when towing, perhaps that photo without one was during build before it was fitted? No draft marks either. The photo of 93 secured at Vospers (therefore probably before acceptance) shows the stern light while the early type fire monitors also show the date of the photo was early on.

I also note one drawing shows the breach hose connectors aft of the cockpit that indicate it to be of later than original build. Similarly the cockpit roof cleats have been re-positioned athwartships rather than the original two being fore-and-aft.

Considering their short operational life, it's surprising how many detail changes were made when all the available documentary evidence is studied! You'd think that after 60+ years all the answers would be known for sure by now!

I would suggest that the light at the top of the mast, while appearing to show all round may actually be masked internally to give the necessary visible angle of 112.5 degs either side of dead ahead. The stern light in the transom will give the 135 deg angle to fill in all round.

The teardrop-like unit on the for'd cabin roof looks more like the style of radio direction finder used by the RAF on their aircraft - the one on top of a Wellington bomber is particularly obvious. A useful fitting for an RAF crash boat? Positioned as it is it could not give the required 225 deg beam if it was a steaming light.

Normal position for a steaming light would be halfway up the mast at about the yard position, but aside from a small unlabelled bracket on the original masthead drawing, I can find no evidence of a light ever being photo'd there. Combination masthead lights for steaming or anchor are common enough today. Perhaps that was how it was?