Andy
My reference for the 'Saar' identification came from JR Angolia and David Littlejohn's 'Labour Organizations of the Reich' published by RJ Bender.
'SLEEVEBANDS (Armelstreifen) Special identification letters were worn on a sleeveband on the lower left sleeve of the service tunic and greatcoat. An order dated 4th January 1939 introduced cuff bands with a single letter to be worn by RAD personnel assigned to work on the Siegfried Line. Yet another order dated 15th March 1939 introduced the letters M, N, O and P. The black band measured 25mm wide and displayed the designation in a machine woven Gothic letter (approximately 20mm high) and with a 5 mm wide and 60 mm long white, silver or gold bar (depending on rank of wearer)on the right and left. These increased by four (H, R, S and T) formed in the western Arbeitsgaue. These cuff bands were cancelled by an order dated 29th April 1941 which refers to them as Armbands with special letters (Armelstreifen mit den Sonderbuchstaben). Known sleevebands are H, M, N, O, P, R(Rhein), S(Saar), T(Trier) and W. These single letter sleevebands appear to have been worn only by RAD units employed on defensive construction.By April 1941 Hitler had no need to think in terms of defence. therefore their use after that was terminated.'
Best regards Simon :cheers: