See also the advertising for
Epiphone,
Fender,
G&L,
Gibson,
Gretsch,
Guild,
Hagstrom,
Harmony,
Marshall,
Martin,
Music Man,
Ovation,
Rickenbacker,
Vox,
WEM
Vintage Leslie advertisements; 10 adverts covering a period of 6 years, from 1969 to 1975. Click the images to have a closer look.

The Most Exciting Portable Speaker Cabinet Ever Designed for Professional Musicians
Leslie Pro 900 - 1969

Belter Weight Champion
Leslie 825 - 1970

Strand Back
Leslie Pro 900 - 1970

The Leslie 950. You Make the Music, It Makes the Show!
Leslie 950 - 1971

925 Has A Power Complex
Leslie 925 - 1971

Fat New Sounds. Skinny Money
Leslie 18 - 1971

Take a Free Trial Run on a Leslie Speaker
Leslie 825 - 1973

Put a Torch to Your Piano with the Leslie Model 60 Speakers
Leslie 60 - 1974

Ignite the Night With a Leslie 825
Leslie 825 - 1974

Leslie. Keith Emerson Says it Doesn't Hurt.
Leslie Amplifiers - 1975
1967 Epiphone Ad featuring a psychedelic fish playing an Epiphone Riviera
1967 Fender Ad - Full Colour Sound
1973 Fender Stratocaster add - The Worlds Favourite Flying Machine
Guitar makers have advertised in music magazines such as Down Beat, Guitar Player and very many more. Some manufacturers advertised widely (Guild, Gibson, Fender) but many more didn't and adverts are few and far between. Here are some of my favourite ads out of the ones i've seen. You can browse through all the images from the category links above, or by manufacturer from the links below.
AMPS
Ampeg, Leslie,
Marshall, Orange, Peavey, Sunn
GUITARS
Epiphone,
Fender,
G&L,
Gibson,
Gretsch,
Guild,
Hagstrom,
Harmony,
Martin, Music Man, Rickenbacker,
Vox