Here's an update:
Got an email from Alan Powell.
This is what he had to say..
I looked up your serial #’s for some preliminary info so here goes;
1352-B Sold on 7/10/68 and built on the same day.
2289-C Now this is a rare one. I always knew the Powell Bikes were hot-I used to race them at Saddleback Park in Orange County, Ca., but this one was literally “hot” it was stolen on 12/13/69 (an early Christmas present) as well as serial # 2292-C. Quick, run out and dust for prints! It was built on 12/5/68 1 of 7 built that day.
2575-D Sold on 3/4/69 and built that same day. 1 of 9
2611-D Sold on 3/8/69 1 of 10 sold to Scooterville. Built on 3/7/69
2899-D Sold on 4/11/69 and built the same day 1 of 16
5054-E Sold on 3/25/70 and built on 3/12/70 1 of 10
5255-E Sold on 5/7/70 to Rent-a-Cycle and built on 5/6/70
6787-JL Sold on 11/24/71 and built on….6/31/71 One of fifteen bikes built that day. Most were model M’s or J’s. Your’s was the only JL. This is one we probably used as a personal bike or for testing as it was not sold until Nov. I probably rode that bike as I was really the only one who test rode the bikes.
6879-L Sold on 8/12/71 to Cycle Town and built on 8/11/71 1 of 3
6971-MO Sold on 9/30/71 built on 9/23/71 1 of 5
I'm making a form to make it easy for Alan to fill in the blanks for the rest of the serial numbers that have been graciously provided.