Rolex "tank" 15 jewel movement but with custom made case

[cmorganw4]

Hi everyone,
I am new to these forums so please excuse any "newbie" mistakes I will probably make!

I have been given the opportunity to purchase this watch:

http://www.ebay.co.uk/itm/1508301254...#ht_976wt_1185

I won the auction without realising the watch was not a born and bread Rolex.

It has 15 jewel movement, however the case has been "custom made."

Is this watch actually worth anything or is it simply worth gold scrap and the cost of the movement?!

Many thanks!