G-5

       G-5 is an agent with British Intelligence.
       That is just a guess on my part. He never expressly states it and towards the end of his recorded adventures he is referred to as an "international agent" but most of the operations we learn about have him working on behalf of or reporting to British Intelligence. He most definitely is at home in Europe which is the backdrop for all but one of his escapades and his obvious command of numerous European languages is extensive and impressive as is his ability to fit in to his surroundings when he feels the need.
       G-5, a man whose real name is not only never spoken but who also eschews the use of aliases, preferring to use his cover designation if a name is required, is a handsome blond haired man likely in his mid-30s based on his depiction. He is in excellent shape and is more than a match for just about everyone with whom he needs to scuffle. He is quite good at boxing and knows a thing or two about the martial arts, throwing and flipping his enemies a lot.
       There is no indication that G-5 has any lasting relationships, at least during the time of his activity, which is understandable since the agent gets around a great deal, surprising considering the state of hostilities around him. With such a wide range of territory, it is not surprising that he does not have a chance to put down any roots. Regarding the territory he covers, a few times he is asked/hired to head to a trouble spot to take care of a crisis brewing but even more often he is just in the right place at the wrong time (for the bad guys).

       For being able to tell a short story in four pages of usually nine cels each, the author, Will Eisner, aka Cory Weyte, was a true master. Of course, that small a space definitely kept the reader from learning anything about the character's history or personality but that was never the intent. Action was, as well as being able to show just how awful the nasty guys G-5 faced really were.
       Mentioned above, the feel of the stories in the G-5 adventures were a good deal grittier and more realistic, bringing to the American comic book reader a better feeling of the fight that was really going on "over there".
       Cory Weyt/Weyte, aka Will Eisner, created two "super agents", X-5 and G-5. They were very much alike and quite a bit different. One was most likely American and the other probably British, though neither were explicitly so marked. They fought different enemies in different parts of the world but they were both entertaining, if not unfortunately both fairly forgettable.
       I wonder if these two heroes might not have been distantly related. After all, they did share the same last number.