I'm not sure Bernie. The descriptions and eligibility page makes mention of a clasp with the title of the second star earned worn on the first, so I don't know if this is the same as a silver rosette, or if that something 'unofficial' or ungazetted? If your father has three stars, then it can't be about standing in for one of them
The eligibility for the France & Germany Star states:
1 day afloat in operational areas of the North Sea in the Royal Navy (provided service was directly in support of land operations)
This as I recall is different from what it used to read, which made mention of being based on the continent for at least one day, which in the case of Coastal Forces, was only ever those units based at Ostend. So the description seems either to have been broadened, or else corrected or clarified. That said, the North Sea would be flotillas based at Ostend or the East Coast, which is Beehive (Felixstowe), Midge (Great Yarmouth) and Mantis (Lowestoft).
If my records are correct your father served on MTB 350, part of the 11th MTB Flotilla, which in the period 1944-1945 was based at Ostend, and I presumably, one or other of the East Coast bases. I assumed returned from the Mediterranean at some point during the timeframe in question and was posted within Home Waters?
Admin