The manufacturer of the card may be printed on the carrier card. When SIM cards are made, they're produced in a standard credit-card shaped plastic card, with a punch-out slot that contains the SIM itself. This outer plastic card may have printing on it that shows who the manufacturer is.
Also, the shape of the circuit pads is proprietary to each manufacturer. Gemplus, the predecessor to Gemalto, used to embed their company name in tiny letters in the copper, at the top of the center area which they shaped like a lozenge. However, I was unable to find a definitive site that shows a catalog of each manufacturer's circuit pad shapes.
You might be able to figure it out by examining pictures yourself. I searched Google Images for "gemalto sim cards" and found a lot of pictures of the circuit pads. Look at the shape of each of the contact pads. Notice how the center pad can be shaped like an O, an 8, a J, it can be rectangular or rounded, squared, or even elaborate diamond shapes. Different card makers have different shapes.
Be careful not to believe every picture you see associated with Gemalto, as many are generic pictures of SIM cards that are being added to articles associated with the current news event. But if you see a picture of a card that has the name "Gemalto" (or other chip manufacturer) printed on the plastic, you can be sure that's the design of their pads.
Regardless of who made your card, you have no way of knowing if the Ki was compromised. Gemalto is just the biggest player in the field, so it's unsurprising they were hit. But that doesn't mean other card manufacturers weren't hit.