As Waidmannsheil and Huvius alredy noted, B 1930 is a George Gibbs, Bristol, serial number. Gibbs used the B prefix on guns they made on bought in barreled actions, stocked, sighted and finished by themselves. The distinctive stock shape denounces it as a Gibbs Mannlicher too. OEWG Steyr sold production overruns of military contract rifles through their agent Auguste Schriever & Co, Liege, Belgium, to the civilian market worldwide. British gunmakers sporterised these rifles in various degrees. Gibbs tore them down to the barreled action and restocked them. Many “name” British gunmakers like Rigby and Purdey bought in such conversins from Gibbs and signed them with their own names and serial numbers.
Yoiur rifle is a Mannlicher model 1892 as originally made for Romania. “Steyr 1893” is the date of manufacture. As Romania changed their order to the simplified model 93 soon, many 92 rifles found their way to the UK. It is a quite early Gibbs conversion as the low serial number shows. 33 is a Steyr factory assembly or serial number. -5 is a factory marking for precise barrel fitting.
About that “black gunk” on your stock: Gibbs often “ebonized” their stock then, that is they stained them black after a then fashion. You may find such black stocks not only on Gibbs Mannlichers, but on Gibbs Farquarsons and shotguns too. Here is a photo of my later Gibbs Mannlicher on a 1899 dated Dutch contract barreled action, Gibbs serial number B 3085. Note the remains of the worn black stock finish.

Another one, from the net. Blackish stock too: