Relief 90's were made in England prior to the dollar pens made in the United states. Originally thought to be named for having sold for 9 shillings and 0 pence, thus the '90' name, and 6 shillings and 6 pence for he model 66, These pens were in fact sold for 5/6 and 7/6 in 1938. The 66 was basically the same as the 90, but had stainless trim as opposed to the gold plated trim on the 90 and came with a plain nib as opposed to the gilt panel and lined sunburst omiridium nibs of the 90.

This is an unusual Relief 90 in BHR with a Relief Fine Osmiridium tipped re-new-point in the fabulous sunburst pattern. Note the spacing between the cap lip and the cap band. US dollar pens in HR had cap bands very close to the cap lip.  Notice the clip is not only gold plated, but has the name relief stamped on the top instead of Esterbrook. See my Boxes page for an original box for these pens.

This is a more uncommon Relief 90 in blue plastic.  These were made in the standard six colors.

Here are two Relief 66 pens in plastic.  These have nickel plated trim and use a simpler nib, whereas the 90's utilize the osmiridium tipped sunburst Relief nibs.

The top pen is at best guess a Relief 66.  There are several things which make this different from the Relief 90.  First of all, while the clip remains the same as the one pictured above, with the word, "Relief" on the top of the clip, the cap on this one is longer than your normal full sized dollar pen.  The barrel is also longer by about the same proportion.  While the lever is also the same, as well as the positioning of the cap band, the top pen is in plastic, not hard rubber like the 90.  In addition, the barrel imprint, which does not reference "relief" or "relief 66" anywhere, utilizes the "Esterbrook" imprint as opposed to the "R. Esterbrook + Co." imprint on the 90.

Here is a shot of both pens open.  Notice the size difference of the plastic relief.  It is quite a bit longer than the 90, its higher priced gold plated cousin.