Are you searching for Irish Merchant Navy Records? As you are posted on the County Cork message board?
Possibly the Latter Day Saints,IGI felt Military Service was the only event type that fit?
If you have found the IGI you definitely should be able to locate at your nearest LDS Centre, However, I suggest you phone as not all Centre have all microfilm, if it hasn't been ordered before from Salt Lake City it might need to be brought it.
It certainly wouldn't be Reserve, the Merchant Navy were not
Military and it took many years before their contribution of bringing goods back and forth to the UK from Canada and the US was recognised.
Military records should be on the National Archive, Kew London website, look for the link to the pay for website where you can now find these records.
You should be able to google, Merchant Navy and find plenty of information.