Photo 4: LBBG sub-adult?, June 17 2001, Missouriweg Maasvlakte, the Netherlands. 

Normally LBBGs don't show very extreme wear on the back by June, but this is an exception. Note the orange orbital ring, where normally this orbital ring is coral red is (in 99,9% of LBBGs). The bill is very adult-like: there is no black on the bill and the red spot extends on the upper mandible. The iris is yellow, as are the legs.
All the abraded feathers are adult-like. 

The inner median coverts, the central scapulars and the mantle were replaced recently.
The primaries have very small tips, p9 even without such a tip and the small white mirror on p10 (just reaching the feather edge) advocate sub-adult rather than an adult. But a strong indication for adultness are the just visible outer primary coverts which appear all-grey. Normally these feathers are the last showing immature characteristics: brownish centres with small white tips in sub-adults (see e.g. image 5).

Note the extreme difference between the stage of the tip of p4 (fresh looking) and the tip of p5 (tip worn away).
The white line visible under the greater coverts are the white tips of the secondaries.