You have a nice set of stamps that would make for a good start in precancel collecting. Unfortunately, none of the stamps are worth any more than a few cents apiece.
Most new collectors have to come to an understanding that just because stamps are "old" doesn't necessarily mean they retain much value, as stamps of the early 1900s were issued in such vast quantities and were used for many years, stamps have flooded the market and only a select number of them retain much value in used condition. As it relates to precanceled stamps, they are often of more interest to specialists who deal in the hundreds of thousands -- or even millions -- of various precancel imprints that were included on stamps for use by high volume mailers.
I would also point out that of the detailed scans you posted, the first scan (showing 2c Washington) is not a precancel but a slogan machine cancel typical for that period; likewise in the second detailed scan, the second stamp (4c Martha Washington) is often confused for a precancel but it is, in fact, a post-cancel, the type commonly used on packages or parcels at some post offices back in the day.
Since you
inherited the collection, it may be that the sentimental value of the collection is much more priceless to you than its monetary value.
If you are looking for more information on precanceled stamps, I suggest you checkout this link which contains a number of good articles to help you better understand precancel collecting:
http://www.precancels.com/getting-started/