TELECOM Digest Editor noted in response to writer:
Many two-piece phones remained in service in the 1950s, especially in coin service. Old B&W TV shows made in the 1950s showed them in regular use. I'm told, however, that the transmitter and receiver elements were actually modern "F" units, not the original types. The sound quality was noticeably better on F units. Someone says the voltage changed as well from early systems. Note too that the 202 type "French Telephone" were replaced with F handsets instead of the E model for the same reason.
Pay phones with the mounted transmitter were simpler since sound induction to that transmitter carried the coin drop bell sounds. The later models required a separate tiny microphone near the bells to transmit the signal.
"F" units were from the 302 series telephone sets. "G" units were from the 500 sets. I don't know about H, I, or J, but K units were used in modern sets where the handset ends are somewhat squared off instead of circular, including late Western Electric units. K and G are not compatible.
And you could turn the vent fan on or off to suit your needs. They almost always had a phone book nearby; large banks had a block of directories. Sadly, most of those old booths are gone, replaced by nothing or wall mounted phones.
A very busy place, like a main train station, had a telephone service center with an attendant and switchboard to assist you in person.
Some newer 1960ish buildings had modern sit down booths made of circular glass or other designs, newer 1970ish buildings just had wall mounted phones in an enclosure. It varied; even in the old days some phones were simply mounted without any enclosure.
Some years ago I visited a former employer and the lobby of the building once held a bank of such phone booths--the chair, table, fan, door, etc. I needed to use a pay phone but the bank was completely gone. The lobby had no pay phone at all! I was directed to another building across the street where I found a wall mounted phone (no enclosure at all) in a narrow back hall. There was another phone and some loud talker was on it. His voice echoed badly throughout the narrow hall and I couldn't hear a thing on my call.
What angered me was that phone booths were supplied for a reason! It was to give the caller some privacy and ability to hear (esp in the days when telephones weren't so good.
Sadly, even in the 1960s vandalism and sleaze took its toll and new installations tended to be free standing or acoustical surrounding only, not a full booth. Some places had a row of pay phones without any separation whatsoever which was absurb for acoustics.
Some train stations have phones subsidized by the carrier so as to provide a 911 emergency service. This is probably cheaper than providing merely an emergency call box, at least the pay phone might generate some revenue to cover its cost even nowadays.
The Bell 3-slot phone was based on the Gray design and Gray built a great many for Bell under Bell specs.
At the rate things are going pay phones will be gone eventually. One factor is everyone having a cell phone. Another factor is that local calls are cheap people will let you use their business lines; years ago that'd be too costly. Years ago employees were forbidden from using employer lines for personal calls, an edict strictly enforced. In those days large workplaces often had payphones on every floor as well as banks in the lobby. Today the lobbies of fancy businesses have house phones offering free local calls.
Of course the telcos by charging exhorbitant rates for pay phone toll calls pushed away a lot of this business. A payphone won't take a real long distance coin call but charge a huge amount $25.00 on a credit card. An regional toll call, which they still carry, runs a dollar or more for a 10 mile call for 1 minute. (Some Bell payphones in Pennsylvania Station NYC offer within-state per minute calls).