My Ad-n-Echo sitting on top of my '64 Fender reverb tank:

A later, three-knob version of the Ad-n-Echo:

(Photo by Marty Wentz)

Here's a Tel-Ray Super Organ Tone:

Tel-Ray's Deluxe Organ Tone:

Later Ad'n'Echo:

Tel-Ray's Echo-Ver-Brato:

(Photo by Woodrow Jackson)

The elusive Gibson GA4RE oilcan delay:

The elusive even more elusive Standel oilcan delay:

Fender's Echo-Reverb:

Fender's Echo-Reverb III:

(Photo by Richard Bills)

Tel-Ray Variable Delay:

Fender's Variable Delay:

(Photo courtesy of Richard Bills)

Fender's Dimension IV:

Fender's rarely seen Dimension IV, large version:

Fender's Multi-Echo:

(photo by Tom Pervanje)

Like the Dimension IV, the Multi-Echo interfaces between an amplifier's reverb send and return and the amp's reverb tank itself.

Tel-Ray's version of the Fender Dimension IV, the Compact Organ Tone:

Here's a solid-state 70's Morley called the Electrostatic Delay Line:

Solid-state 70's Univox Echo-Tech:

"ADINEKO" Label found inside all oilcan effects:

Solid-state 70's Univox Echo-Tech:

The seldom-seen VOX Echo-Reverb:

"Vox" Label - note the manufacturer and patent numbers: