I gave myself a B, which represents the average of an 'A+' reading lead sheets/charts, and a C sight reading written bass lines.
I came from many, many years of piano lessons and a few years of gigging on keyboards, so sight reading anything was a pretty standard skill for keyboard player. However, the big band thing was almost over by the time I started playing bass professionally (in the mid 70's), and I never developed the amazing reading and playing skill on the bass that would be required to, for example, nail a Broadway type show by sight. The gigs I have done over the last 25 years or so primarily involved reading charts, and a few bars of written out bass lines in some cases when a specific part was required.
I can actually read treble clef much more quickly and accurately than bass clef at this point, since on a lead sheet, most of the rhythm cues and I guess actually the entire charts, are written in the treble clef.