It's a Sonaro bass cab w/ 15" Eminence speaker. I can't make out the date code on the speaker but it may well be the original, since Sunn used Eminence extensively. Sunn debuted this cab in early '69. Previous to that it had a 40W head mounted to the top of the unit as a combo but still was set up as a fully enclosed reflex cab.
I have five different Sunn rigs -- play 60's/70's "classic rock" guitar. The setup that is probably my favorite sounding is a '69 Solarus head (the 60W version) with a '69 Sonaro cab which I've modded the baffle to load a JBL D130 (not D130F) and two 10" reissue Jensen C10Q's up top. That wide front-to-back bracing board had to come out to get the 10s to fit so I used a 1 by 3 brace and it works fine for guitar to dampen back vibration. The different tone signatures of the JBL and the Jensens complement each other awesomely, resulting in an incredibly smooth and wide range tone.
What are you playing thru the Sonaro and how do you like it?