I know you may be tired of me saying this, but steak is too expensive to guess whether or not it is properly cooked. You should always use an instant-read meat thermometer to ensure your meat is cooked to the perfect temperature.  For a recipe like this, I like to use two meat thermometers. First, I use a DOT oven alarm with a probe. Then, I set the target temperature, insert the probe in the thickest part of the beef, not touching the bone, and then an alarm beeps when the desired temperature is achieved. As additional insurance, I also use a Thermopen instant-read thermometer. When my DOT alarm goes off, I verify that the beef is at the proper temperature by inserting the temperature probe into different parts of the steak. No guessing here and possibly ruining a perfectly good steak by overcooking it.  Meat thermometers are relatively inexpensive and available online or at most grocery stores. Please do yourself a favor and get one if you don't have one.  If you don't have a meat thermometer, the only way to see if your meat is done is to make a small cut into the center to inspect it visually.