Hey hope all is going sweet over there on the West Coast.. I have been looking through some buttons of Levi's and I can not come up with this style of flat button you found.
Picture 2 shows the buttons used during the Era: 1902 ~ 1928 period.
This is a black donut top button used on the LEVIS 201XX Lot. No. 2 jeans. It is considered the most basic style of top button by Levis with " LEVI STRAUSS & CO * " stamped on it. Only Black button to be found on levi's will be from this era. Very Rare.
Picture 1 shows Era: 1930 ~ 1941 period, 1945-Modern Peroid.
The donut core was filled and molded into a solid heart top button for the 501XX series. Levis decided to include it's country of origin, and thus, " * S . F CAL * " was inserted in together with the other characters. This button is the father of the modern button used currently.
Just from the look of the print which that lettering of style was used in the 1920s til about 1929 I would say this button could be from about 1920-early 1930 but this style of print is also used alot during the 1960s. But again I have not been able to find this style button, all the other levis buttons are easy to find.