Some different types of keys for your perusal.

Antique keys in the library of the former San Franciscan convent in Guadalupe, Mexico. Locking up a church in Laguardia, Spain with the ‘Big Key’.
Part way along the road to Rouen we spotted a church with an unusual steeple. When we stopped to take a photo of it a man came running up and asked us if we’d like to see inside. He opened up the door to the old church with an ancient-looking key.‘We cut keys’ sign in Hong Kong.A Rodin sculpture of a man holding keys at the Portland Art Museum, Oregon. Cross Keys Inn pub sign in Gloucester, England.And a few other keys: Piano keys in black and white in the Aalborg Art Museum in Denmark.Telegraph keys in a display of historic postal artifacts in the Palacio Postal in Mexico City. More of Frank’s Tuesday Photo Challenge: Key.