Hello
You say:-
Technical Data plates:
1) Bigger plate size (50 x 70 mm):
TYPE: 683
DWG. No.: I G 1372
SERIAL No.: R3/LB/185 560
CAPACITY: PORT
INSPECTION: R3 45H
MAKER'S No.: -----
DATE: ------
2) Small plate size (63 x 31 mm):
IDD RR
DRG No.: R3/211-3
SERIAL No.: 1425
INSPECTION: No.: ALV 70 R
The Inspection number will usually be maker / manufacturer and 45 will likely be the Inspector.
See Manufacturer codes:-
http://spitfirespares.co.uk/reference3.html
See also the following thread:-
http://www.rafcommands.com/archive/17733.php
Inspection number
The forum thread not only has a list of various Manufacturer Codes by Elliott Smock of the Rebuild a Whitley Project, but a post by a former Inspector of another aircraft type the AW Whitley, regarding the Inspection number on the plate ...
"For example, mine was AW99A Meaning Armstrong Whitworth Aircraft Co. My personal number being 99."
You know where you found the parts (the location) and therefore you must look for, find and trace all local records in local and national Archives of the country where the crash occurred and also in the archives of the country of the occupying forces, at Town Hall, District Administration, Archives, Museums, Libraries and other places of deposit
which were created at the time of the crash to trace a record of a crash at that location. Fire service, Undertakers, local Town Authority, your equivalent to our War Committee, Military units, Police, Observers in the area, etc., etc., to get even a date (or several dates) to start or begin with!
I would never trust books or internet entirely, most are not detailed enough to give a field/nearest road location anyway and my research in original documents and cross checks with MoD, indicate that some authors have copied the errors and mistakes of others.
This may surprise you, but my detailed research in early WW2 for several August 1940 days, day and day/night Ops in ORBs of Squadrons, Groups and Commands, indicate that the dates on some Loss Cards upon which Chorley based some of his bomber losses are incorrect! The MoD were unable to explain why some Loss Cards had wrong dates, or had been recorded on non-standard Loss Cards.