In Star Trek: Discovery season 3, episode 6, "Scavengers", the appearance of a Type 2 phaser from Star Trek: The Next Generation's era creates a plot hole in regards to Emperor Philippa Georgiou (Michelle Yeoh). Since jumping to the 32nd century, Star Trek: Discovery has been able to incorporate the full scope of Star Trek, all of which now happened in Discovery's distant past. So far, there have been shout-outs to Star Trek: Voyager and Star Trek: Deep Space Nine; the Type 2 phaser in the episode seems to be another cool Easter egg but the fact that Georgiou knew what it was is problematic, although there is an easy explanation.
In "Scavengers", the ex-ruler of the Mirror Universe accompanied Commander Michael Burnham (Sonequa Martin-Green) on an unsanctioned mission to the planet Hunhau, which is controlled by a faction of the Orion and Andorian syndicate called the Emerald Chain. Michael's goal was to rescue Cleveland "Book" Booker (David Ajala), who had been taken prisoner, and to retrieve a black box from a starship that was destroyed by the Burn. Georgiou and Burnham pretended to be in the market for spare parts from Hunhau's massive junkyard full of scrap from across the galaxy so Tolor (Ian Lake), the Orion who oversaw Hunhau's Emerald Chain facility, toured the Terran Empress and the rogue Starfleet Officer around his scrapyard.
As a cover to search for Book, Georgiou and Burnham claimed to be looking for "pre-2400 items", including self-sealing stem bolts, which were next to the plasma coils - all references to TNG era Star Trek technology. But when Tolor showed Georgiou a Type 2 phaser (which had a curved handle like the phasers used in DS9), the Empresses immediately scoffed and said, "Please, half of those parts didn't even exist in that era" before she showed off a functioning 23rd-century tricorder. While these were fun Easter eggs for Star Trek fans to spot, how did Emperor Georgiou, who time-traveled aboard the U.S.S. Discovery from the 23rd century, instantly recognize what a 24th-century Starfleet phaser was? After all, she completely bypassed the TNG era, as well as the next 800 years, before landing in 3189.
The easiest explanation for Georgiou's anachronistic knowledge of 24th-century Starfleet weapons can be found in Captain Saru's (Doug Jones) log at the start of "Scavengers" where he noted that three weeks had passed since the U.S.S. Discovery arrived at Starfleet and the United Federation of Planets' secret headquarters. In those three weeks, Discovery was retrofitted with 32nd-century technology - and this is ample time for Emperor Georgiou to have read up on everything she missed in the last 930 years.
Further, downloading intelligence about the Federation's last millennia of history is exactly something the Terran conqueror would do; not only is Georgiou a former agent of Section 31 (who is earmarked for her own spinoff), but back when she ruled the Mirror Universe, Emperor Georgiou already knew about the Federation because she had access to the U.S.S. Defiant's files. Georgiou inherited control of the 23rd century-era Constitution-class starship, which accidentally ended up in the 22nd-century Mirror Universe and was captured by the Terran Empire in the Star Trek: Enterprise season 4 two-parter "In a Mirror Darkly".
Emperor Georgiou is an old hat at acquiring any edge she can get over her enemies (and her allies), and she very likely kept herself busy during the 3-week time jump by studying up on 930 years of Starfleet's technological advancements and history. Therefore, a 24th century-era Type 2 phaser wouldn't impress Georgiou. Meanwhile, tactics like these are what make Emperor Georgiou so dangerous and are why she was targeted by Section 31's mysterious Agent Kovich (David Cronenberg), who is likely the culprit of the traumatic flashbacks that are now incapacitating the wicked Terran warlord in Star Trek: Discovery season 3.