The primer 'patches' correspond with the exact design/position of the doublers (apparently removed at scrapping for whatever reason exposing the lower primer prepared skin or for that matter in process of being fitted to return the acft to service (unlikely!) ) that are fitted in due course and common to all B737-200/300/400/500 Boeings for that matter as appropriate to and in accordance with the Boeing (or Airbus or whoever's) 'Aging Aircraft Programme' Airworthiness Directive/Supplementary Structural Inspection (and associated Service Bulletins, documents and mod. programme). Together with other preventative structural mods. also driven by AD's/ASB's once the aircraft reach approx. between 14 and 20 years old - these ongoing structural sampling and modification programmes are common to all manufacturers/types, Airbus, Boeing and whomever - they are not a joke and if you dont like them then there wont be many of these 737's 200-500's that you'll be able/want to fly in
http://www.airweb.faa.gov/Regulatory...F?OpenDocument
http://www.airweb.faa.gov/Regulatory...7?OpenDocument
http://www.airweb.faa.gov/Regulatory...D?OpenDocument
The damage to the FR aircraft (as I understand it from reliable sources) involved removal of masking tape (after painting?) with a stanley knife badly scoring the skins for which there was a repair scheme possible involving skin replacement but eventually deemed uneconomic to implement