Waterman, in 1953, were the first company to use a resilient plastic cartridge as a fountain pen ink reservoir, a system that was to be adopted by all the major manufacturers and is now the standard filling mechanism.
The Waterman's CF (for cartridge filler), was the first pen to offer the cartridge/converter option but this unmarked pen must have been made around the same time as the clip is clearly stamped 'Watermans'. The 's' was dropped from the imprints in 1954. The shape of the clip is also very similar to the Waterman's Junior pens produced towards the end of the 1940s.
The pen is finished in classic black with gold filled clip, cap ring, and barrel end stud. It is in excellent condition throughout and has been serviced and tested. The nib is hooded, in the style of the Parker 51, but it has an unusual 'facet' at the pointy end.
An issue with the Waterman CF, and this pen, is that the cartridges and ink converters are very hard to come by. Fortunately this pen has an original cartridge fitted which can easily be refilled using a syringe. I have filled the cartridge with Parker Blue/black ink and it works very well, giving good ink flow and a medium line, perhaps a little on the fine side. The pen will be sent with the cartridge in place so it is ready to write. At 13.5 cm. capped and 15 cm. posted it is a very good sized, slim and quite elegant pen.
I think this pen must have only been made for a very short time, it may have been produced in order to test the cartridge system before it was released in the CF. Sometimes pen manufacturers did not put a model number, or name, on a pen that was not going to be around for long, many 'wartime restrictions' pens are similarly unmarked. It is a rare pen.