His CRS10 Form will contain much of the information that is in his DIS A (seamans book) but also probably more.
I wonder if this is your uncle: Robert Vart, Date of Birth 25/6/1916, Service Number 1058258 If so he has a file in BT391/110/115 here: http://urlx.org/gov.uk/4f2ceCVART&accessmethod=0
These records detail the sea service record of merchant seamen engaged in the liberation of Europe (6 June 1944 to 8 May 1945). They give the seaman's name, discharge 'A' number, rank or rating and qualifications together with details of the ships on which they served.
His CRS10 Form may be held in the Fifth Register of Seaman's Service
in piece details BT382/1845 here: http://urlx.org/gov.uk/e0bcc
Note the Fifth Register will only give service from 1941. Prior to that, his service may be recorded in the Fourth Register and that is not online but I can give details if required.
If you hit the link and then "Request this" and follow instructions. You need to be specific and ask for the CRS10 for Robert Vart 25/6/1916 born Jarrow.
The cost is £8.50 for up to 10 pages delivered to your email address within 24 hours on a no find no fee basis.
If you think the first link I gave is your uncle then following that link and the instructions will also cost £8.50 because it is a separate file.
I hope that helps
p.s. There is a medal listing for Robert Vart also at the TNA Kew in this file: http://urlx.org/gov.uk/a7993
This is available for £3.50.