Dan Rainey (Active 1930s - 1960s)
'Rainey' was briefly a cover artist around 1960-62 who worked for Badger Books and Digit Books. When I (Steve Holland} was having a dig around for information, I stumbled upon the work of Dan Rainey, who is quite possibly our artist. Rainey is described as Irish and his watercolours flourished in the 1930s. I'm not convinced this is an accurate description as, elsewhere, at least one piece of artwork to be found in the Ulster Folk & Transport Museum dates from 1977.

The signature visible in the painting of a small coaster is certainly similar to the signature to be found on some of the covers below. A search on Google also turns up some prints of the Titanic.

An auction in 2013 at RDS Clyde Hall, Ballsbridge, Dublin, included a collection of 10 albums, 7 of which contained "historical recollections and research by Dan Rainey, 35 watercolours and various photographs and documents. Articles include East Belfast characters, Holidays in Dublin and Portrush, a collected history of Holywood, childhood memories of Ballymacarret in the 1920s, the Connswater Flute Band, etc." The final three albums contained a total of 129 watercolours and pen and ink drawings of historical buildings and locations throughout Ireland and also ornithological drawings from the 1930s. Another auction included 204 large watercolours and pen and ink drawings, 8 small watercolours and 1 oil painting of ships that passed through Belfast, all contained loosely in albums. Another album comprised 19 pages of watercolours of ships ensigns, flags and colours.

Apart from saying that it still needs to be confirmed that cover artist Rainey is Dan Rainey, all I can add is that Rainey's cover for Dashiell Hammett's The Glass Key was based on an earlier cover by De Seta
(click: http://2.bp.blogspot.com/_XsVALQtGIZM/TNiCl9TrlwI/AAAAAAAAS6A/I3Ggotjtf9U/s1600/Digit-nn+Hammett+Glass+Key+%28small%29.jpg)