David,
Your point and pictures are most interesting. The second shot is quite unique by it's sharpness and preserved colors.
I won't be able to answer your query about production dates; I can only notice that the type of camouflage shown by "Gelbe 2", KG(J) 27 at Kaufbeuren does show on a majority of Erla machines, be it in the 150 - 152, 490 - 491 and 770 blocks. The ones known to me and illustrated by pictures are listed here as follows:
A: W.Nr. 150 XXX - 152 XXX
1. Bf 109 G-10 W.Nr. 150'816 "Schwarze 4", 6./JG 2, Langensalza, June 1945.
http://www.flickr.com/photos/2809206...57625208099917
2. Bf 109 G-10 W.Nr.150'87. "Weisse 15", Germany, summer 1945. Source: Noro 2009, p. 173.
http://www.flickr.com/photos/2809206...57625208099917
3.Bf 109 G-10 W.Nr. 150 889 "Weisse 7", 1./JG 27, Risstissen, May 1945. Prien, Rodeike and Stemmer 1998, p. 506.
http://www.flickr.com/photos/2809206...57625208099917
4. Bf 109 G-10 W.Nr. 151'035, "Grüne 2", I./JG 301, Germany 1945. Source: expired Tonelli auction.
http://www.flickr.com/photos/2809206...7625208099917/
5. Bf 109 G-10 W.Nr 151 567, "White 13" 1./JG 300, Wunstorf , April 1945. Source: Noro, H. (2009) "LO+ST", Dainippon Kaiga, p. 33
http://www.flickr.com/photos/2809206...7625208099917/
6.Bf 109 G-10 W.Nr. 152'043 "Weisse 57", Central Germany 1945, Hlidebrandt 1988 p.17
http://www.flickr.com/photos/2809206...57625208099917
B. W.Nr. 490 xxx - 491 xxx
1. Bf 109 G-10 W.Nr. 490'137, "Weisse 14", 15./JG 51, Hptm Waldemar Wagler, Rinkaby, May 1945. Source: forcedlandingcollection.se
http://www.flickr.com/photos/2809206...57625208099917
2. Bf 109 G-10 W.Nr. 490 383 "Rote 17", Lt. Josef Jordan, 6./JG 300, before 14 January 1945. Prien and Rodeike 1995, p. 158.
http://www.flickr.com/photos/2809206...57625208099917
3. Bf 109 G-10 W.Nr. 490 621 "Bianco 3-11" 3a. Sq. I. Gruppo Caccia, Lonate Pozzolo, April 1945. D'Amico and Valentini 1985, p. 98
http://www.flickr.com/photos/2809206...57625208099917
4. Bf 109 G-10 W.Nr. 490 629 "Gelbe 7", Lt. Werner Petereit, 7./JG 3, Garz, 11 March 1945. Prien and Stemmer 1996, p. 386.
http://www.flickr.com/photos/2809206...7625208099917/
5. Bf 109 G-10 W.Nr.490 642 "Rote 2", 2./JG 300, Pilot Fw Gzik.
http://www.flickr.com/photos/2809206...7625208099917/
6. Bf 109 G-10 W.Nr. 490 655 "Gelbe 24", Lt. Anton Wöffen, Staka 6./JG 27, near Rheinberg, Germany, 11 March 1945. Source:
http://www.asisbiz.com
http://www.flickr.com/photos/2809206...7625208099917/
7. Bf 109 G-10 W.Nr. 490 755 "Blaue 1", 8./JG 3, Garz, 1945. Prien and Stemmer 1996, p. 390.
http://www.flickr.com/photos/2809206...7625208099917/
8. Bf 109 G-10 W.Nr. 491 213 "Grüne 12", Ofhr. Bruno Klostermann, 11./JG300, Jüterbog-Waldlager, Autmun 1944. Lorant et Goyat 2005, p. 115.
http://www.flickr.com/photos/2809206...7625208099917/
9. Bf 109 G-10, W.Nr. 491 320, "12 nero", serg. Carlo Cavagliano, 4a Squadriglia, II Gruppo Caccia, Northern Italy, before 12 February 1945. Beale, D'Amico and Valentini 1996, p. 169.
http://www.flickr.com/photos/2809206...7625208099917/
10. Bf 109 G-10 W.Nr. 491 354 "Giallo 2-2", 2a Sq. I. Gruppo Caccia, Lonate Pozzolo, April 1945. D'Amico and Valentini 1985, p. 98.
http://www.flickr.com/photos/2809206...7625208099917/
11. Bf 109 G-10 W.Nr. 491 356, Magg. Adriano Visconti, I. Gruppo Caccia, Lonate Pozzolo, April 1945. D'Amico and Valentini 1985, p. 92.
http://www.flickr.com/photos/2809206...7625208099917/
C. W.Nr. 770 xxx
1. Bf 109 G-10 W.Nr. 770 293 "Gelbe 67", Rinkaby, 12 April 1945. Hitchcock 1977, p. 10.
http://www.flickr.com/photos/2809206...7625208099917/
2. Bf 109 G-10 W.Nr. 770 313 "Schwarze 3", Gatow, 1945. Source: Bergstrom and Pegg 2005, p. 188.
http://www.flickr.com/photos/2809206...7625208099917/
3. Bf 109 G-10 W.Nr.770 376 "Schwarze 9", NAGr 15, Liberec 1945. Source: Bergstrom and Pegg 2005, p. 186.
http://www.flickr.com/photos/2809206...7625208099917/
Actually, the ones with late war standardized tails which seem common with the K-4 camouflage pattern are very rare. The only one I know about is Bf 109 G-10 W.Nr. 491 300, Gardelegen 14 April 1945. Luftwaffe im Focus 2, p. 34.
http://www.flickr.com/photos/2809206...57625208099917
There is to my knowledge at least another Erla G-10 color picture extent, found here:
Bf 109 G-10, Erla type camouflage, Germany, 1945. Source: WW2incolour.com
http://www.flickr.com/photos/2809206...in/photostream
Hoping for a timely publication on those Erla built G-10's ;-)))
Cheers
Marc