Yeah, I agree with Alieno too...but I don't think it's just one '39, I think that it must be two '39s. "In the year of '39 assembled here the Volunteers" This is the year when they left, possibly in 2039, probably not 1939 considering they didn't have rockets then. "In the year of '39 came a ship in from the blue" Then this is the '39 when they came back, but you don't know how long they were gone for, so they could've been gone for 100 years, then it would be 2139, or maybe 500, or maybe even 1000 so it would be 3039!
Yeah, I agree with Alieno too...but I don't think it's just one '39, I think that it must be two '39s. "In the year of '39 assembled here the Volunteers" This is the year when they left, possibly in 2039, probably not 1939 considering they didn't have rockets then. "In the year of '39 came a ship in from the blue" Then this is the '39 when they came back, but you don't know how long they were gone for, so they could've been gone for 100 years, then it would be 2139, or maybe 500, or maybe even 1000 so it would be 3039!