It is a plectrum banjo with the long neck, but it is "Chicago tuned". The strings match the top four on a guitar. Band members who had to switch between guitar and banjo did not want to learn a new chord structure, so they started tuning the banjos to match the guitar.
Andrew, when ever I was around Al he played regular 6 string Spanish Guitar. Perhaps you were thinking of Carl Kress? Carl (like many of the early Jazz Guitarists started off on Banjo. His original tuning was Tenor all the way across. Starting with a very low Bb then up to F then C then G and D and A. but fairly soon he changed the top 4 to Plectrum -- Bb - F - C - G - B - D !! Haven't you heard or seen the wonderful Entertainer Maty Grosz? If you haven't you've really missed something. Marty and I grew up together back in my "Chicago Days". And Oh! Marty plays the Kress Plectrum tuning. Eddy Davis