Currently know option codes used on Lowlights:

M001:  Cannot be identified: Mentioned on Belgium made coupe with VIN 1753160
M018:  Larger reflector in brake / indicator light  (see for example the birth certificate from Tomas)
M020:  Mph speedometer (see juni 1958 parts manual p9-28)
M067:  77Ah battery, 6v (see for example the birth certificate from shane 57)
M076:  Headland for Holland only  (see juni 1958 parts manual p9-07)
M124:  Headland for France only (see juni 1958 parts manual p9-07 and p9-08)
M128:  White wall tires. (see for example the birth certificate from Laurens)
M138:  Mounting Assembly for Sealed Beam Headlamps (see juni 1958 parts manual p9-07, p9-08, p9-09, p9-19, p9-20 and p9-30)
M139:  Sealed Beam Headlamps (see juni 1958 parts manual p9-09)
M157:  Unknown (might be an electric windshield washer set up) , mentioned on Bernina blue convertible with VIN 1999690 and VIN red coupe with VIN 2078020
M355:  US Equipment (see for example the birth certificate from Laurens) 
M473:  Cannot be identified: Mentioned on Belgium made coupe with VIN 1753160 

M577:  Top Light grey (Option on L41 Black and L428 Graphite Silver convertible's)
M578:  Top Black (Option on all convertibles) 
M579:  Top Light-Green (Option on Amazon green convertibles) 
M580:  Top Sahara-Beige (Option on Colorado Red convertibles
M581:  Top Texas Brown (Option on Diamond grey convertibles)
M582:  Top Blue (Option for Bernina blue convertible) 

M584:  Cannot be identified (mentioned on Graphide silver convertible) 
M585:  Upholstery Leather and Polster Red Brown (Option for Black and Pearl White convertibles)
M586:  Upholstery Leather and Polster Green Grey (Option for Amazon Green convertibles)
M587:  Upholstery Leather and Polster Light Beige (Option for Colorado Red convertibles)
M588:  Upholstery Leather and Polster Brown (Option for Graphite Silver convertibles)
M589:  Upholstery Leather and Polster Honey Brown (Option for Diamond Grey convertibles) 
M590:  Upholstery Leather and Polster Blue (Option for Bernina Blue convertibles)
 
M593:  Upholstery full Leatherette Red Brown (Option on Black and Pearl White convertibles)
M594:  Upholstery full Leatherette Green Grey (Option on Amazone Green convertibles) 
M595:  Upholstery full Leatherette Light Beige (option for Colorado Red convertibles)
M596:  Upholstery full Leatherette Honey Brown (option for Diamond Grey convertibles) 
M597:  Upholstery full Leatherette Blue (option for Bernina Blue convertible)
M598:  Upholstery cannot be identified 

M950:  Laminated Glass Windshield  (see juni 1958 parts manual p8-41)
M951:  Exterior Rear-View Mirror (see juni 1958 parts manual p8-51 and p8-52)
M952:  Bumper Overrider Bars (see juni 1958 parts manual p7-04, p7-05, p7-06, p7-07, p7-08, p7-09, p7-10 and p7-11)
M958:  Cannot be identified, Probably steering damper
M986:  Cannot be indentified on a 59 Coupe with VIN 2406329


But one thing is strange:
On the different lowlight birth certificates I have seen, option M951 is mentioned as "Ram protection" or in German "Rammschutzstangen",  but in the parts manual that should be M952. Besides, option M952 was only available after January 3, 1958 production, so VIN 1522121 can't possibly have ram protection, but can have the exterior rear-view mirror.

To me it looks like Stiftung AutoMuseum Volkswagen is wrong in quoting M951.