Yeah, private eye era was when rye was the default whiskey. Bourbon didn't really start to rise until post WWII, I want to say. That's why rye's contemporary comeback has coincided with the return of so many classic cocktails (and apparently a lot of alliteration, too).
But Philip Marlowe drank gimlets.
“I sat down two stools away and the barkeep nodded to me, but didn’t smile.
“A gimlet,” I said. “No bitters.”
He put the little napkin in front of me and kept looking at me. “You know something,” he said in a pleased voice, “I heard you and your friend talking one night and I got me a bottle of that Rose’s Lime Juice. Then you didn’t come back any more and I only opened it tonight.”
“My friend left town,” I said. “A double if it’s all right with you. And thanks for taking the trouble.”
He went away. The woman in black gave me a quick glance, then looked down into her glass. “So few people drink them around here,” she said so quietly that I didn’t realize at first that she was speaking to me. Then she looked my way again. She had very large dark eyes. She had the reddest fingernails I have ever seen. But she didn’t look like a pickup and there was no trace of come-on in her voice. “Gimlets I mean.”
“A fellow taught me to like them,” I said.
“He must be English.”
“Why?”
“The lime juice. It’s as English as boiled fish with that awful anchovy sauce that looks as if the cook had bled into it. That’s how they got called limeys. The English – not the fish.”
“I thought it was more a tropical drink, hot weather stuff. Malaya or some place like that.”
“You may be right.” She turned away again.
The bartender set the drink in front of me. With the lime juice it has sort of a pale greenish yellowish misty look. I tasted it. It was both sweet and sharp at the same time. The woman in black watched me. Then she lifted her own glass towards me. We both drank. Then I knew hers was the same drink.”