This recipe is a broad interpretation of Jacob A. Didier's 1909 original and the Casino recipes that follow in Hugo R. Ensslin's 1916 book and other subsequent...
Interesting range of comments with respect to Difford's vs "original" version which if I interpret comments correctly, differ over primarily how much Maraschino / sweetness one prefers in this drink. I always start with the Difford's recipe and did so in this instance notwithstanding usually avoiding cocktails with orange juice. To my surprise, presumably because of the lemon, I found this to be a lovely and well balanced cocktail. Not too sweet, and for me more importantly, not too orange forward. I will compare to the "original" recipe at some point.
The Didier/Ensslin recipe is more to my liking and reminds me much of my ideal Martini profile (orange bitters, lemon), just with a bit of added sweetness from the maraschino (and flavor) and the Old Tom (Hayman's). The orange juice and larger measure of maraschino in the main recipe here just seems to dilute the gin botanicals and intensify the maraschino beyond what I prefer. To each their own.
I've managed to find an earlier instance of the casino cocktail; on page 5 of "The Reminder" by Jacob A. Didier (3rd Edition) from 1909. It seems Ensslin copied Didier (the wording is almost the exact same).
3/4oz maraschino sounded like it would taste of nothing but maraschino so I went for 1/2oz and an additional dash of grapefruit bitters. Very nice, very soft, and even at 1/2oz the maraschino is starting to overwhelm. 8.5/10, HOF Challenge 7/291
Didn't have Old Tom, but use The Botanist Islay Gin. It was wonderful. Nice balance to the cocktail. Did follow the advice, and sip and swill in my mouth. It gives it a spice, pepper flavour just drinking doesn't release. Very good cocktail.
Built with Bombay blue sapphire otherwise as prescribed. It was a bit tart but tasty. I might cut back on the lemon a bit say 1/4 to 1/3 oz and replace with a bit more gin. Overall quite tasty and would recommend it to a friend.
My go to Gin is Pinnacle Gin for mixed cocktails and it has a slightly more tempered taste so that might work as well.