Jim Perry has compiled a list of Luftwaffe claims that is more complete than the older files done by Tony Wood, and is integrating a part of the job done by Jochen Prien and co in his Jagdfliegerverband series.
You can find them there:
http://don-caldwell.we.bs/claims/tonywood.htm
According to this list, the 200th JG 2 victory to be confirmed was :
18/07/1940Hptm.WolfgangSchellmannStab II.JG 2BlenheimN. Le Havre13.15935yesOKLPrien/Bock
And the 500th was:
24/04/1941Uffz.KasparAmhausend1.JG 2SpitfireN. Théville16.075270yesC.2036/IIAnerk: Nr.63Prien/Bock
But given the long time the Luftwaffe took to confirm a victory claim or not, I'm not sure at all that the celebrations for the JG 2's 200th and 500th victory were on this date, probably earlier.