While you could buy the new 70th Anniversary JBL 4312SE for $2.5k, the original 4311B from the late 1970's is a professional monitor that was built to last. If you find a pair that has been reasonably well cared for and not overdriven, they can deliver satisfying and even insightful sound, especially from music produced during that period. On average, they sold for about $350 each back in the day...which translates to around $2k for the pair in 2018 dollars making these, although well used, quite a bargain.
The 4311 and Pioneer HPM 100 are what sparked my interest in audio when I was in my late teens, so when I saw this pair in good condition on eBay, I just had to take a chance on them. I have greatly enjoyed many trips down memory lane during the three years that I have owned this excellent pair, but it's time to find them a new home to make space for new gear.
If you live in the San Francisco Bay area, I'm happy to set up a time for you to come by and audition them before purchase. You'll also save on shipping with local pick-up. Otherwise, I will have these professionally packed to ensure that they arrive in the same great condition that they left.
I do have functional bright blue grills for them, but they are not original. I'll include them at no extra cost, but if you are a collector, you will likely want to replace them.
Regarding condition, all of the drivers look almost brand new (see the photos) except for one midrange which has a small dent near the bottom edge of the dust cover. The high-pass capacitors on the mids and tweeters appear to be original and could probably stand to be replaced. The pots all function correctly and without static after a few turns. The spring speaker terminals all work great. I'm including the gold pin-to-banana plug adapters at no extra cost.
The previous owner explained to me that these were at one time installed in a recording studio. There are carefully patched holes in the cabinets that you can see in the photos. These were the mount-points for studio installation. They don't affect the sound and suggest that this pair has some fascinating tales to tell about recordings they were used to create. Thanks for your consideration.