when were the BoN P-47D-22 and BoB P-47D-28 introduced?

[zan64]

I spent an evening researching to but no avail. So like the title, does anyone knowwhat month/season the P-47D-22 (in game razorback) and P-47D-28 (in game bubbletop) introduced? thanks!

[LukeFF]

D-22: before April 1944. 

 

D-28: late July/early August 1944

 

You can research P-47 serial numbers here: http://p-47.database.pagesperso-orange.fr/Database/42-2xxxx.htm