Artillery headstamp identification

Having acquired this shell, I am at a loss to positively identifying it - Headstamp does not allow this old chap to research it ! Help please!!!
'F27 x 145 DM 1001 LOT R-61 - 101-X
Any thoughts out there?

27 x 145 is the ammunition type: for 27 mm aircraft gun as used by Tornado aircraft, fo example. Also used in a naval mount (Marine-Leichtgeschütz, MLG).
DM1001 is the German model number of the case (DM = Deutsches Modell)
Looks like made by Radway Green (RG), but the experts will have to decipher the lot number. 1961 would considerably predate the adoption and therefore is too early.

Thank you JPeelen - I gave you little info, didn’t mention the steel case, or indeed that the headstamp looked untouched! I’ve added a full pic of the shell.
Excellent one! Thanks.