@ davidships: funnel marking says" P & M 1945, with that 1945 probably referring to the date of manufacture. Would "military" build possibly refer to ex US Army or US Navy tug?

Dirk, do you have other pics showing better what is on the funnel apart from "1945" - the main design? "P8...", perhaps.

And what about the "name" on the lifeboat "..ETA YU"? Could be irrelevant, but does that mean anything to you?

I assume that there is no public record of US State enrollments. Perhaps the brokers can tell you more?
http://www.usedseattle.com/classified-ad/1949-Burlington-Marine-Tug---Iron-Horse_27006978

When she was for sale at Seattle last year, she was described as "1949 Burlington Marine Tug", "heavy duty military build with rebuilt Cat (D 318) engine"
42 x 15 x 5ft..

I think that "Burlington Marine" refers to where she was for sale, or worked - cannot find any reference to a builder of that name.