I came across a fascinating website , filmsinfilms.com which features advertising for films within films. The advertised films are often, but not always, from the studio who made the film being viewed.
Henry Fonda in DAISY KENYON . The Greenwich is showing MR LUCKY and WOMAN IN THE WINDOW.
While Daisy KENYON is from Fox in 1947, the other two films are from RKO, 1943 and 1944.
From WOMAN ON THE RUN in 1950. The cinema is showing two other 1950 films, THE BIG LIFT and FORTUNES OF CAPTAIN BLOOD.
All three films from 1950 but three different studios, Universal, Fox and Columbia. So maybe sometimes it’s just an accident?
From WHITE HEAT. The Drive-In is showing SOUTH OF ST. LOUIS and SIREN OF ATLANTIS. All from 1949. One from Warner Brothers, one from Universal.
.
A nice touch from DREAM BOAT (1952) . Clifton Webb plays a former silent film star who resumes his career and stars in Sitting Pretty (which Webb had made in 1948. )
Fred Clark, Ginger Rogers, Clifton Webb (and Anne Francis in the row behind.)
From Phantom Lady (1944, Universal), SWISS MISS is from Hal Roach/MGM in 1938.
This wonderful marquee for Creature From The Black Lagoon (1954,Universal) was from The Seven Year Itch (Fox, 1955)
Vienna's Classic Hollywood 
And near the start in Sam Fuller’s 1964 film “The Naked Kiss”, Constance Towers walks past a cinema marquee showing “Shock Corridor”, Fuller’s previous film with Ms Towers.
That would be no accident! Well spotted.
So cool!
Very interesting,thanks for the link.
I take it that you are familiar with the “Reel Streets” website.
In the nifty little Noir SOUTHSIDE 1-1000 there is a shot of a cinema showing
RED RIVER a nod, perhaps to DOP Russell Harlan and editor Christian Nyby.
Brit flicks are full of scenes involving cinemas here’s a few of my favorites:
In THE BLUE LAMP the Coliseum Cinema Edgware Road is showing
GRANNY GET YOUR GUN.
There’s also a shot of the London Pavillion showing ESCAPE ME NEVER.
I understand ESCAPE ME NEVER also pops up in NIGHT AND THE CITY.
In GIRL IN THE PICTURE the credits show the Regal Hammersmith
showing TARANTULA!
WALK A TIGHTROPE shows the Odeon Westbourne Grove
showing THE WAR LOVER.
Finally in THREE STEPS TO THE GALLOWS a bus passes advertising
the latest 3D sensation HOUSE OF WAX.
Thanks, John. that is so interesting.
Sorry Vienna,I forgot my favorite of them all,especially being
a native North Londoner.
In THE ANGEL THAT PAWNED HER HARP at the very start
of the film there is an extended tracking shot down Islington
High Street. First,we pass the Gaumont and can clearly see that
it’s showing THE FAKE supported by
RAIDERS OF THE SEVEN SEAS.
Then further down the street on the other side of the road there
is an enormous hoarding advertising another 3D sensation
SANGAREE.
Wonderful. Good memories.