The Waterman 503 was one of the new range of pens introduced after the end of WW2.  In addition to pens for general use the 503 series also included two 'special purpose' pens:  the 'Shorthand', and the 'Bookkeeper', this pen.

The Bookkeeper 503 was fitted with a firm, extra fine nib, needed for the small letters and numbers that the job required, and often the use of carbon paper. 

In addition to 'private' customers, Waterman catered for the large commercial users, companies that employed hundreds of office workers needing to use fountain pens on a daily basis.  To facilitate selection of the right pen for the job they devised a colour code, a white cap stud for a firm, fine, 'Bookkeeper' pen and a red cap  stud for the 'Shorthand' version. 

Judging from the condition of this pen I'm confident that it was not a 'company' pen but bought privately.  It shows few signs of use and has clearly been well cared for, it could be described as 'near mint'.

The pen has been fully serviced and tested.  No restoration, as such, was needed although a new ink sac was fitted as the original had hardened with age.

The pen is in excellent condition, it has a first class surface and strong barrel imprint.  The white cap stud, probably hard rubber, is also in good condition, which is unusual as they are prone to cracking.  It is very unusual to see the 'Book-Keeper' label still intact and in perfect condition, a very good indicator of sparing use.

The 'white top' bookkeepers pen is the least common and most collectable of the 'special purpose' Waterman 503 pens

The 14 Ct Gold Watermans no. W2A nib writes with a smooth extra fine line.  It would be a good choice for someone with a small 'hand' or for more detailed work and perhaps, drawing. 

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The gift box is brand new, it will serve well for transportation, protection, and display.