The Mabie Todd Swan lever filling pen was first made, in England, in 1920 and the company quickly became recognised as a leader in the manufacture of 'self filling' pens. The early pens were made in hard rubber and sometimes had flexible nibs, as in this example. 

The pen has been fully, but conservatively, restored to good working order.  The hard rubber has attained a faint brown patina due to the natural oxidation of the surface layer of the rubber.  The surface is good and the imprint is very clear, there are faint remnants of a longitudinal line pattern just visible on the cap.

At well over six inches when posted for use this is a very long, slim, and elegant pen, typical of the design that was most in demand at the time.  It is also a very light pen, another important consideration as the pen was made to be used for extended periods of time.  A light pen is much better suited to protracted use as it is less tiring for the small muscles in the fingers and wrists.

The filling system works well and the 14 Ct. Gold nib writes with a medium line, with light pressure it flexes to a broad line to give good width variation and add character to the writing.  When used 'conventionally', and quickly, it delivers a finer line with the lightest of pressure.

The box has seen better days but it is probably the original and should be kept with the pen. 

Although this Mabie Todd Swan self filler is clearly an impressive and adept writer it is probably best to use it as a 'signature pen' for letter writing and other occasions when time allows for the writer to enjoy getting the best from the pen.  Pens of this type should be enjoyed rather than just used.