In the early days of US sales, Glock sales reps were directed to specifically target sales to police departments. They understood that whatever guns the police chose to carry would inevitably be picked up by the general public as well. It was a good strategy and one that has proven more successful than anyone could have imagined. By the mid nineties, upwards of 60% of US departments were issuing Glock firearms as the standard duty weapon for their officers. Not much has changed in the last twenty-five years–except for the various calibers, models, and generations that the uniformed officers carry. While it would be nearly impossible to track down every variant that has been issued–many are not even specially marked or might only have special serial numbers–here is a collection of ones known to exist:
A Brief History of Glock Firearms Aimed at Collectors 