Vox also offered another bass that was derived from the Saturn IV.   This model was the Apollo IV. It added battery operated onboard effects: treble and bass booster, distortion booster, and G-tuner.

The 1968 "Vox Musical Instruments - The Sound That Travels With the Stars" catalog described the V281 Saturn IV bass as follows: "An exciting all new four-string Florentine cutaway bass guitar. All new easy-to-fret fast-neck with Vox double T-bar and adjustable steel rod. Two graceful holes in matching white binding complement the arched top. Fully adjustable bridge with special arrangement for forward or backward adjustment of strings, providing perfect in-tune fretting. One volume and one tone control. Sunburst."

A hardshell case was included.

The 1968 US Vox price list indicated that the retail price of the Saturn IV was $255 USD. In today's dollars, the Saturn IV would retail for about $1625.

The Saturn IV bass was produced for Vox in Italy by EKO in Recanati Italy. A decal on the back of each guitar states: "Made for Vox in Italy."

EKO made Vox guitars for the US market were first shipped to the American distributor of EKO, LoDuca Brothers Musical Instruments Inc in my home town of Milwaukee WI. After inspection, the guitars were then forwarded to the American distributor of Vox, Thomas Organ.