LR have been known to mix-and-match (including fitting Tdi engines for TD5-era British military vehicles).
Whether the grill protrudes or not is no indication of era. The protruding grill indicates whether the vehicle has factory air conditioning. Air conditioning in the Tdi era in Australia was dealer/importer fitted. The factory Tdi air was the same as the County and even LRA knew how bad that was. Every vehicle without air conditioning has the flush grill, from the County through to the TD5.
It is believed (which we all know that can be very wrong) that no Tdi Defenders went into Army service, through some were trialed. I saw a trials crew-cab Defender 110 Tdi in the flesh, and it had a split rear tailgate/hatch (essentially Series 3 style). Looked quite similar to this vehilce internally. IF this was a trials vehicle accepted into service then the rear door may have been upgraded to the TD5 version on the other vehicles.

