Anyone ever seen this: missing engine code stamp

[kinggeorge13]

So I was working on my 1975 tin top "camper" this weekend and was checking to see if the engine code matched up with the age of the bus.  It's fuel-injected and manual trans.   I'd say 1/4 - 1/3 of the buses I've owned came to me with a replaced engine with a code that was (usually) significantly newer than the year of the bus.  So I always like to check.  However, it appears to have no engine code stamped into the case.  I've never seen one missing before.  And usually they are stamped pretty darned deep into the metal.  I only cleaned it with cleaner and rag.   But as you can see from the photo below, it's blank.   Fairly sure it's not a recent brand new engine from someplace because the buildup of oil/dirt/grease looks exactly like every other 40 year old VW engine I've seen that has not been cleaned up.   This is what it looks like:


I would have expected something like this:


Anyone seen a blank one before?

Thanks!

[BUSDADDY]

Look on top of the case near the left front, close to where the bellhousing flange starts.

[kinggeorge13]

Working on it.  Found a mouse nest.   Twigs.  Like big twigs.  How the heck do twigs get up in there?  Cleaned most of that out but not exactly certain where I'm looking (I understand the general area, just not exactly the location that the 1/2" x 2 stamping will be under the black hard burned oil/crap which means I have to clean my way down to bare metal.  I'm assuming not under the engine tin, though.....   I'll do some research tonight to see if I can find some photos of the exact location.   

There is a BIG "However" though.   For sure this is a 1975 bus.   This photo below is from under the transmission.   I don't have a lot of experience with 5 rib transmissions but would this not be a 6 rib transmission?  (photo directly below is of my transmission from underneath):


I always am never sure what counts as the 6th rib, especially from underneath but compared to others, it seems like this is a 6 rib transmission.    A classic 6 rib tranny photo I've seen that shows how the ribs look along the bottom and sure looks exactly like mine to my old eyes:


Anyone agree mine is a 6 rib transmission? (the first photo, not the 2nd photo as I'm using the 2nd photo for reference of what a 6 rib transmission should look like)

Thanks!

[BUSDADDY]

Sure looks like one from here, I wonder what kind of combination of starters, bellhousings and flywheels you have?

Here's the alternate engine code location for 411/412 and Porsche:

[kinggeorge13]

Ok, now I know exactly where to look.  Just two characters but that's all I need.   Meanwhile, I have a theory on the history of this bus and it's based on a little conjecture that is based on a fairly decent likelihood and a few findings and suppositions.   Here we go:

Facts:
1973 tintop bus.  ( I see I originally wrote 1975 in the original post but that was incorrect.   Too many buses.)

Current setup inside bus as bought by me:
Cabinets installed were installed by a previous owner and is the configuration used in the 1976-78 Standard Campmobile (no stove)
Transmission is a 6 rib (confirmed today) 091.  So that is not original
Engine "tin" (the thick part around the fan) is stamped as a "GD" which would be a 2000cc solid lifter engine from 1976/77.   I realize that sometimes the tin is not mated with it's original engine but stick with my logic and I think I have compelling evidence of what it all is.
Engine is all VW Fuel Injection.

Based on all this, I'm going to suggest someone gutted a 1976/77 Standard Campmobile bus and moved the camping interior cabinetry/bed, the GD engine and it's matched 6 rib 091 transmission engine into their 1973 bus.

But here is the biggest clue for me as to narrowing in on the exact age of the transposed parts.  The AFM is a 6 pin 280 200 018 which was mostly used '74-'75 but I've seen info that some early 1976 buses also had this AFM before they changed over to the newer 7 pin AFM 280 200 018 later in 1976.   

So I'm going to state that it's very likely the engine, transmission and camping interior all came from an early 1976 bus and are now in my 1973 bus.