Leigh Kitchen, who is also a forum member, has previously posted officers wearing the grenade above a bronzed collar but attributed them to RMA rather than RME on another forum:
http://gmic.co.uk/topic/37275-the-royal-marines/?page=4
The officers' grenades are of the RE/RA style (without the ubique scroll) and are not the universal grenade that started the thread off.
For members information an excellent pdf on all RM badges is here:
http://www.rm-badges.com/images/Cap%20Badges.pdf
Alan