Established in 1840, the Hazelton piano company was originally called the Hazelton Brothers after Henry and Fredrick Hazelton, who began making pianos in New York City. Until the turn of the 20th century, the brothers manufactured pianos that were sized as grands. Then the upright piano craze gave rise to Hazelton uprights, which were found in many living rooms in and around America. They then added baby grands -- which are still sought after today. The Hazleton brand faded from production in the 1950s, but is being reinvented as an overseas import piano by Samick of Korea.
Start with the obvious by looking for a decal on the inside of the keyboard cover. Look closely to see if it has a faded presence in the varnish. Chances are you'll be able to make out the label's remains in the piano's finish.
Examine the sheet music stand. Most times, a quick glance will help you narrow down whether or not you are dealing with a Hazelton piano, as the company's music stands were usually scroll-cut openwork and quite elaborate.
Check the interior of the piano. On the metallic soundboard, you will see "HAZLETON" in raised letters.
Determine a specific year's make and model by looking through old Hazelton catalogs. These can be found either through your local librarian or by contacting a piano restorer. You can also find images online by searching through an image database of pianos and scanned catalogs.