"It's not a Sanborn map. The numbers on the map reference individual buildings, not larger zones."

From the pictures provided, it's hard to tell; however, after looking a little closer at it, I think that you may be right that it looks like some sort of destination map. I used to use one similar to that in a former position I had to get around the city proper way back in the day. Perhaps contacting the city planning department? [[ I know, but just don't laugh too hard ). I may have a copy of it buried deep in the home archives.