this is the cities official address street from block 2129 which is,pachako, 2029, and this is maintained by the first floor on this building and this has the official address of the city. the date the address was issued and maybe the date the address was changed and other alternate addresses we may initially applied to the building. when you look for the history of your building not only do you look at every address it might have been called by. example you might ask for both streets it intersects and always reference block 21, 29 block or block 1f. we're referencing blocks and addresses are nothing but trouble. people make them up. they come and go. 1125 abc. we have tremendous problems so use blocks primarily. >> in addition to map's there's other resources showing characteristics of lots that are very valuable resources. that's title companies. your title companies the major ones in san francisco, all have original copies of the assessors block map's and changes to those individual blocks which include lot line adjustments and ease meants that often make all the difference in whether