lamont:
Mad Men had a very substantial set budget, which got more substantial as time went on. The problem is, the set people were dealing with the trickiest period of all - the recent past.
It's comparatively easy to do Civil War or medieval stuff, because you're creating a world that is very different from our own - mistakes jump out at you.
But the '60s had so much in common with our own era that it's easy to forget to check every last little thing - it's hard to remember that traffic signs were often different than today's, Smokador urn-type ashtrays were seen in grocery stores, food cans had a top and a bottom seam, etc.
And it's easy to fall into the trap of assumptions. On Matlock, which is set in my native Atlanta but which was filmed mostly in L.A., all the cars have lovingly-replicated Georgia license plates, accurate in every detail. Except that the California prop guys didn't know that Georgia doesn't use front plates like their state does, so they put their handiwork on the front and rear bumpers of every vehicle, at least until Atlanta newspapers started razzing them about it. It probably never occurred to anyone to check, because front and rear plates are just "the way it is" in most places.