This is a large batch of slides that originally came from an estate sale and appear to have belonged to a locally well known photographer from the Spokane Washington area and later Northern Idaho named Leo Oestreicher. He was known for his portrait, landscape and postcard photography. His career started in the 1930s and he died in 1990. These slides contain a lot of landscape and portrait photos but also a lot of photos from day to day life and various vacations around the world. Here's an article on him from 1997 which is the only info I have found on him: http://www.spokesman.com/stories/1997/jan/04/photos-of-a-lifetime-museum-acquisition-of-leo/
Many of these slides had the date they were processed stamped or printed on them. I've found that in cases where I could verify the date (e.g. there is a handwritten date), that this date has typically been the same month the photos were taken. I expect that in MOST cases these photos were taken relatively near the processing date.
Slide names ending in 'a' are raw slide scans, those ending in 'b' are scanned with color restoration and Digital ICE, and those ending in 'c' are scanned with color restoration and dust removal (medium setting).
Dates in the form of '1955-03' indicates a date stamped on the slide, probably when it was developed. Dates in the form of '1955-XX-XX', '1955-03-XX' or '1955-03-02' indicate hand written dates (e.g. 1955-XX-XX indicates '1955' was written on the slide.)