Toronto. For Christmas 1951 I received the gift of a Brownie Hawk-eye kit with a camera (box), a roll of 620 film, flash bulbs, flash-gun, dry cells for the gun and a plastic protector to hang over the flash-gun in case a bulb exploded. There was a wave of amateur cameras with synchronization for flash bulbs in the late 1940s and 1950s and lots flash-guns to choose from like this Heiland model.
The built-in flash mentioned in the ad is the synchronization to shoot a flash bulb at the right time as the shutter opened. This was before the days of built-in flash that we see today, even in smart phones. The flash bulb was the obvious solution to indoor photos with the abysmally slow media of the day. Flash bulb popularity lasted about two decades before cheap electronic flash-guns were offered and later built in flash (first bulbs, then electronic) Most modern day digital cameras and smart phones have built-in electronic flash and many high end cameras can take external electronic flash too.
Thanks to George Dunbar for mentioning this wonderful LIFE magazine ad for a Heiland flash-gun accessory (LIFE February 19, 1951 issue).