I would check with title and go to the city and see if there are copies of permits for the extra 1/2 bath. Sometimes half baths don't appear on public records but they are on title or on file with the city. It can make a difference on the appraisal and will help reassure buyers that it was done with permits.
If the half bath is not permitted, now might be the time to go to the city to apply for a permit. Hope this helps.
Let me know if you have any other questions. I have 2 clients/friends of mine that are leasing a place in Hancock Park over the next several months but will be looking in the Cheviot Hills area for 3 bedrooms or more and over 2,000 square foot home to buy in the $1.5M range and under shortly. If your property fits this description It would be great to hear more about it if you are thinking about selling.
Keller Williams Realty