Gibson instruments in the 1970s often did not have the most intuitive of controls, especially when compared to their competitors; but this was integral to the broader tonal palettes for which they strived. Varitone equipped guitars had been part of the Gibson line since the 1950s, and the newer Norlin period guitars and basses were less intuitive still; many late seventies musicians were simply not getting the most out of their instruments! So it is no surprise that Gibson attempted to educate owners with printed material and even vinyl records.
Summary of EB3 varitone controls
The following sheet (produced by Norlin in 1978) shows Gibson's description of series 2 EB3 controls. Older series 1 controls are similar, though not identical.
See also the equivalent sheets for the Gibson Ripper, Gibson G3, Gibson RD Artist and Gibson Les Paul Signature basses.

At this point the EB3 bass was right at the end of it's production - just 184 guitars shipped in 1978, compared to a peak of 2421 in 1973 (see the EB3 shipping statistics); the guitar pictured is in the rarer white opaque finish, only available between 1976 and 79.
Gibson EB3 bass for sale
Gibson Vintage EB-3 Bass with slotted Headstock 1969-1972
Smithtown, New York, 117**, UNITED STATES OF AMERICA
$1600
1972 Gibson EB-3 Short Scale Electric Bass Walnut Finish SG Vintage Gig Bag
Astoria, Oregon, 971**, UNITED STATES OF AMERICA
$1995
1974 Gibson EB-3 Bass Cherry Red ~ All Original ~ USA +OHSC 1970s
Jacksonville, Florida, 322**, UNITED STATES OF AMERICA
$1997
This EB-3 is in very good condition, showing player wear with buckle rash, dents, and scratches as expected from a well-loved vintage bass. The neck is straight, action is comfortable, and it delivers the fat, thumping low end that these ... more
Vintage Early 70's Gibson EB3 Electric Bass Guitar
Fresno, California, 937**, UNITED STATES OF AMERICA
$2600
This Bass only shows cosmetic wear due to time and being played on. Bass sounds incredible and could use a good home. Bass is stock and fully original including the finish, and no modification's
Every used instrument we have has been play tested
Make sure to contact us with any further questions!
... more
1972 Gibson EB-3 Slotted Headstock Vintage Short Scale SG Bass Walnut w / Case
Seattle, Washington, 981**, UNITED STATES OF AMERICA
$2900
Surprisingly versatile, the EB-3 delivers warm, midrange rich snarl from the mini humbucker in the bridge position, and powerful low end thump from the neck position "Mudbucker " The rotary pickup selector offers a bevy of tones at the flick of a ... more
Gibson Electric Bass EB-3 Slotted Headstock 1968-1972? ~ Excellent Cond!
Jacksonville Beach, Florida, 322**, UNITED STATES OF AMERICA
$3000
Gibson EB-3 Cherry Mod 1969 Electric Bass Guitar Original Case Slotted Head Art
El Segundo, California, 902**, UNITED STATES OF AMERICA
$3500
... more
1969 Gibson EB3 Bass Guitar- 100% Original with Original Case
Glastonbury, Connecticut, 060**, UNITED STATES OF AMERICA
$3700
"1973" Vintage Cherry "GIBSON EB-3" with OHSC Serial #056076 in Great Condition
Riverside, California, 925**, UNITED STATES OF AMERICA
$3795
1965 Gibson EB-3 - 100% Original - Straight Neck - Low Action - Great Player!
Dayton, Ohio, 454**, UNITED STATES OF AMERICA
$4000
Comes with the original case and candy as shown. ... more
Gibson EB3L Bass Guitar- 1968 / 72 LONG SCALE SLOTTED HEADSTOCK WITH Case
Hagerstown, Maryland, 217**, UNITED STATES OF AMERICA
$5000
CHERRY FINISH, CHROME METAL TRIM, BLACK PICK GUARD.
LONG SCALE WITH SLOTTED HEADSTOCK, # 914058 ENGRAVED ON HEADSTOCK.
NOT THE ORIGINAL CASE, IT WAS BOUGHT IN 1992. PAPERWORK INSIDE CASE.
BASS HAS NICE GLOSS CHERRY FINISH, COUPLE OF MARKS, NOTHING MAJOR. VIEW PICS.
COMES WITH STRAP, 2 CORDS, MASTER KEY CHROMATIC PITCH INSTRUMENT, EXTRA PLUG JACK, KEY FOR THE CASE
ANY QUESTIONS PLEASE ASK, ... more
1971 GIBSON EB 3 SLOTTED HEADSTOCK BASS CASE - Made in USA
COLOGNE, GERMANY
£385
* CASE ONLY !
* interior has stains
* tolex has rips
* all latches are working fine
* worn but solid
* check all pics
... more
Gibson EB 3 CASE 1971 - passend für NUR GESCHLITZTE SPINDELSTOCK-Version
COLOGNE, GERMANY
£399
* CASE ONLY !
* strap that holds case open=GONE
* bottom and top are loose =need reglueing
* tolex has rips
* all latches are working fine
* check all pics
* SOLD AS IS - NO RETURNS... more
1971 GIBSON EB 3 SLOTTED HEADSTOCK BASS CASE - made in USA
COLOGNE, GERMANY
€439
* CASE ONLY !
* interior has stains
* tolex has rips
* all latches are working fine
* worn but solid
* check all pics
PLENTY of PARTS for SALE
ATTENTION! OVER 1000 more
GUITARS-BASSES-AMPS-PARTS
in our OTHER AUCTIONS !!!
CHECK OUR SHOP OUT -------------->>>>>-------------->>>>>
... more
1971 GIBSON EB 3 SLOTTED HEADSTOCK BASS CASE - made in USA
COLOGNE, GERMANY
€444
* CASE ONLY !
* strap that holds case open=GONE
* bottom and top are loose =need reglueing
* tolex has rips
* all latches are working fine
* check all pics
Over 1000 more
GUITARS-BASSES-PARTS in our OTHER
AUCTIONS !!!!
TAKE A LOOK !!!... more
Gibson EB-0 - EB-3 Bass Slotted Headstock 1971 Immense Sound!
Salford, M6***, UNITED KINGDOM
£1894
Not quite sure what the extra pickup is but it sounds monstrous and a really useful contrast with the factory pickup especially with a standard three way switch. The conversion has been done very nicely
Obviously been played but plays very nicely with recent set up, strings and electrics checked
I really like the slotted headstock which is... more
Gibson EB-3 Bass Guitar 1967
Horncastle, LN9***, UNITED KINGDOM
£2950
Do you have an equivalent sheet for the Victory Artist bass # what the switches do # thanks how do I get a copy
Hi bassman85 - this series of info sheets was printed in 1978, some three years before the advent of the Victory bass series - the equivalent information appears on page 16 of the 1981 victory bass owners manual, which is reproduced here http://www.vintageguitarandbass.com/gibson/catalogues/1981_Victory_owners_16.php