In the casino scene, Michael Strong is reading a French-language newspaper. The headline reads "Mais Oui, On Peut Manger du Cheval". The English translation is, "Of course you can eat horse".
The re-used photo booth sequence could be easily explained, within the story universe, as being one of the regular places Jim knows he will find the IMF mission assignments. He always has the key, and seems to know what to do without hesitation to get the assignment. (Reusing the briefing sequence was done several times over the 7-year run of the series as a way of saving money when they went over budget.)
This episode uses the same opening sequence of Phelps driving in close-up, then getting his assignment in a photo booth as the episode "Operation Heart".
All three major guest stars in "The Emerald" were series veterans. William Smithers (Tomar), who had earlier appeared in The Ransom (1966), made his second and final appearance here. Also making his second and final appearance was Claude Woolman (Williams), who was previously seen in The Legacy (1967). Finally, Michael Strong (Petrosian) turned in his third of four series appearances, having earlier guest starred in The Trial (1967) and Operation 'Heart' (1967). A couple years would pass before Strong would make his fourth and final appearance in the fifth season story Decoy (1970).
To get an idea of how high the stakes were when they were gambling, every $1,000 bet was equivalent to about $7,500 now after adjusting for inflation.