This long service medal was awarded to naval officers serving as naval engineer in the navy. This branch was established when sailing-ships where decommissioned in favour of ships powered by steam. The medal was first issued in 1905 and abolished in 1948 when the branch was integrated into the corps of technical officers.
The medal itself is exactly the same as the regular long service medal for officers. The ribbon however is blue-white-orange-white-blue whereas the regular ribbon is orange-white-blue. The medal on the left is for 25 years of service (XXV).