Can anyone I.D this engine?

[dieselfumes]

I have a 79 300cd. I suspect the engine is not original,1 It has a transmission vaccume valve mounted on the IP (not hooked to anything) but my transmission doesnt have a modulator valve. 2 it takes the pencil type glow plugs. This makes me think that it must have a newer then 79 engine,but it does not have an egr valve! can anyone tell me what year this engine is by these numbers?or point me somewhere to look them up? 617 912 12 105 499
P.s this is the BEST website ever! I have learned more here in 3 hrs then in 3 weeks searching the other mercedes sites!