Marshall overstrung piano

[cas562]

I have a Marshall, 6 octave, overstrung piano. Photos attached (hopefully!), It was originally sold by Murdoch of Dover. Is this Marshall the same as Marshall & Sons or Marshall & Rose?
I was once told that it is a yacht/ship piano but I am not sure about that.
I would love to know how old it is but any info would be gratefully received.

[Bill Kibby]

I can find no record that any maker ever described an instrument as "Ship's piano", this seems to be an invention of the internet. A Yacht Piano is a small upright with fold-away keyboard. Yours is in the style of the 1930s Minipianos, but I am surprised to see the Marshall name on its own.
There may be a date label hidden under the keys.