H.M.S. 'Barlow' was one of the ubiquitous "Bar" class boom defence vessels introduced in the late 1930's as one of several ship types associated with harbour defence. Sufficiently large to be employed overseas as well as in Home Waters, the "Bar" class ships were all built to the same basic specifications; namely, 730 tons displacement, 174 feet long overall, coal-fired, and armed with one 3in. gun. 'Barlow' herself, built by Simons at Renfrew in 1938 and designated Z60, served twenty years until sold for breaking in 1958