You are so right.
Several years ago, I spotted a Martini-Henry bayonet for sale in a local antiques mall, with stalls rented by various dealers. The tag on it said, "Civil War bayonet, $65." When I told the store cashier that it was a British bayonet from the 1870's, she replied, "Well, that's in the same era." It really bothered me. That mall went out of business about a year later, hopefully before some poor tourist got schnookered.