• Stargate SG-1 S5E3 "Ascension"
• Stargate SG-1 S4E20 "Entity"

In "Ascension", Orlin gifts Sam a sizeable emerald, claiming it to be her birth stone, implying that her birth month is May. But in "Entity", we saw that her birth date is actually in December. While I assume this was just a production mistake, if I had to come up with an in-universe justification for what we see here, I would have to assume that Orlin was just mistaken. Maybe he saw someone else's birthdate marked somewhere and he assumed it was Sam's, or he read a chart wrong and thought December was emerald. Looking at various price charts for birth stones, I see that the December stone sometimes varies, but it is always on the cheaper side of birthstones. On the other hand, May is always emerald, which is one of the most expensive birth stones. Regardless of how Orlin had made the mistake, I figure that Sam was aware that May is always a more expensive stone than December and decided not to correct him at all and just cash in on the mistake. She needs a new microwave and toaster.