Not enough info, but want to cite it anyway

I really should post this circumstance on the Ancestry errors wiki--and will--but I also need to figure out how to cite it.

In Ancestry's "U. S. City Directories (Beta)" I have accessed what they call "Stockton City and San Joaquin County Directory, 1888." In it I found my subject individual working as "hostler" for a particular man whom (with a little additional research) I discovered was somewhat well known in horse-racing circles. This is an interesting bit of information and I want to use it.

So I went to the first image in the series to find a title page and it turns out that the microfilm title for the series is actually "City Directories of the United States: 132422 Stockton CA 1888, 1889, 1891, 1893, 1896, 1896." 

So I started paging through to see where it divided. It appears to be only 1888 and 1889, the paginations seem right and consistent for those two directories. However, the second one contains a rainfall table for Stockton that spans the years 1889-1898. Clearly, this section of the book at least appeared in or after 1898--which year does not appear in the titles anywhere.

So although I cannot accurately date the information that this individual was a hostler in Stockton for the horse-racing gentleman, I want to use the information. 

Any suggestions on how to cite this? The glutinous mass that I have created to date looks something like this:

"Stockton City and San Joaquin County Directory 1888," digital images, <i>Ancestry.com</> (http://www.ancestry.com : accessed 8 April 2012); first image of the file labels it "City Directories of the United States: 13242 Stockton, CA [California] 1888, 1889, 1891, 1893, 1895, 1896," and credits the Library of Congress with holding the originals. However it appears that images 1-139 pertain to 1888, and the next issue, though labeled 1889, may actually be 1898, as it includes a rainfall chart for Stockton, 1889-1898. The latter section contains an entry for Charles F. Walker, hostler, possibly in 1898, but the year is uncertain.

Janis Walker Gilmore

Pawleys Island, SC