The majority of Schlage locks will have the company's name stamped into the exterior face of a deadbolt. Check the external side of your door to see if you can find the name stamped on the lock. If you cannot find the name on the deadbolt face, take a close look at the latchplates. Latchplates are the plates found on the edge of your door that surround the latch or bolt. Schlage locks will often have the company name stamped into the latchplates as well.
There might be the company's name stamped upon the lock cylinder as well. This is the area you would insert your key to unlock the door. However, keep in mind that if it is stamped on the lock cylinder, the writing will be tiny.
You may also want to check the key you use with the lock. Schlage keys have their unique shape, called a "key blank." Check the Schlage resources section to find what a Schlage key looks like and compare your key while also checking for any stamps on the key.