My guess is that it's an older set. I purchased my plans and spoke with Paul Moore a little over a year ago. I was not sent 5100 series prints. I received 48-01 to 48-30, size 11 x 17. Also received 48-00 series sheets 2 and 3, size 22 x 34 they are just nice to have, Paul Moore said if you get aggravated you can throw darts at them! Also 5200 series sheets 1-5, and the 5300 series sheets 1-3. The 48-29 and 48-30 sheets are for the base plate, and stick magazine. Also received a thick packet of parts description, materials list, and basic guidance. Hope this helps.