These pens came in three basic sizes: standard, small, and oversize.
Canadian production also included a long standard, which is scarce.
Taking advantage of the new filler design, these pens were translucent, allowing you to see how much ink remained in the pen at any point (the ravages of time and ink exposure have made most surviving Vacs rather opaque, although you will still find lightly-used or new-old-stock examples with good transparency).
US production continued through 1948, and until 1953 in Canada.
Although other patterns were used, Vacumatics are strongly identified with the laminated celluloid which they pioneered.
The best of the Vacumatics are the top-line models of the '30s, as illustrated above.
The filler units are all-metal, the nibs are two-tone, there is a "jewel" and tassie ring at the end of the barrel, and both jewels and the section are laminated (at the end of the decade, many pens came with nonremovable "bullseye" barrel jewels, which appear black in light that is less than bright).