With regard to the cap badge. The brass cap badge with kings crown was the standard issue to Royal Marines prior to the coronation of Queen Elizabeth II the officers cap badge was split with a separate crown. Two badges were issued, one polished for general wear and one dull for use in the field.
After the coronation the Queens crown badge replaced the Kings crown version but it was not until the mid 1970's that the dark bronze badges for working dress wear and stay bright for formal wear, were introduced replacing the brass badges.
With regards to the 3 Cdo Bde insignia on the square. It is worn by all members of 3 Cdo Bde regardless of qualification. Army and RN commando's wear either Army Commando, Royal Navy Commando in addition to the red on blue commando dagger (this is the only issue version) with the green beret. Royal Marines Commando wear a black on green shoulder flash which replaced the red on blue Royal Marines Commando in the 1990's.
Prior to 1990 the Royal Marines Reserve wore a small red on blue R under the RM Commando shoulder flash but this is no longer worn.
There was a red on blue Royal Marines flash worn by Phase II Royal Marines and Royal Marines Reservists and non commando trained instructors with the Royal Marine Cadets (these instructors also wore an SC red on blue square under this shoulder flash)
Royal Marines band service had their own shoulder flash first type in red on blue and now black on green. They used to wear the green beret but no longer do, wearing instead, the old blue beret with red tombstone backing (as used by the Royal Netherlands marines). At various times there have been special band cap/beret badges for the band but they are no longer used.
Wings four types are in use on the old CS95 or current MTP uniform either standard RM wings or more recently the SBS wings. In addition APJI wings are sometimes used.
Each Commando has a reconnaissance troop which is parachute trained, the brigade reconnaissance force is also parachute trained whilst the SBS is of course parachute trained.
The SBS has its own signal squadron, it is entirely Royal Marines retaining their beret badge rather than the later SBS beret badge. Having passed the special forces communicator course they wear the new style special forces communicator wings.
Most Royal Marines wear a green or sand working belt, but sometimes the RM stable belt is worn. The RM signallers with the SBS wear the 18 Signal Regiment black stable belt or green SBS stable belt.
Hope that is of assistance and sorry for replying to such an old post.