Bulova 1959 Bulova 23

I know it's a Bulova 23 made in 1959. Beyond that I've seen this style referred to as a Mystery Dial. Below the 12 o'clock position the face reads "Bulova" and below that "23 Jewels". Above the 6 o'clock position the face reads "Selfwinding". On the back of the case starting at the 12 o'clock position and moving clockwise are the following inscriptions: "Bulova"; "Self Winding"; something small and hand inscribed that looks like "B427"; "Shock Resistant"; "L9"; "Anti Magnetic"; "Water Proof". A case serial number is also present. It is E044049. Above that, below the "L9" the case reads "14 KT Gold".  The watch is running. I have not opened the case as I'm not sure if it's a twist off or pry off. There appears to be a space to pry on the side opposite the crown but applying pressure with a plastic pick did not open the case. I didn't want to be anymore aggressive without knowing how this opens.  This watch belonged to my grandfather who I believe bought it new. Possibly from Ziegler Jewelers in Highland, IL where he purchased other jewelry. The watch was passed to me by my father. To the best of my father's recollection, this watch hasn't been worn since early 1980.