Replacement speedometer

[mbz.280sl]

I did a search and looked in the technical manual but couldn't find an answer to this.
I bought a used VDO speedometer with the number 1215420906 on it.
Can I use this as a replacement for my 1969 280SL?

Thanks,

[al_lieffring]

This is the parts book page for the 190SL instruments.
The 121 542 09 06 number is shown as being subbed to 121 542 13 06

I don't know it the gages for a 190SL are the same diameter, of if the cable would fit either. Also the 190sl gage is most likely 120 mph max not 140.

I imagine this part could be quite valuable to someone with a 190SL, but I dont think it would be a good match to a 280sl.

[mbz.280sl]

Thanks, Al.
The speedometer does show up to 140MPH and dimensions appear to be the same as my existing one.
I'm traveling right now and won't return until after Thanksgiving so I'll do some more checking when I return.

Thanks for any  further information anybody can provide.

[mbz.280sl]

I've found out more information about my replacement speedometer and Mercedes speedometers in general.
I'm not a mechanic so bear with me.
The speedometer in my 1969 280 SL (believed to be original) shows VDO on the lower center face, below that to the right it shows 0020.
I don't have the speedometer out of the car so I don't know what numbers might be on the back.
I e-mailed Gernold at SL Tech in Maine to ask about the replacement speedometer that I have and as Al said it's for a 190 SL.
The dimensions appear to be the same for the 190 SL as the 280 SL and they are both 140 mph. 
Gernold also said the correct speedometer for a 280 SL is 004 542 5806, that's a bit confusing to me since mine just has the numbers 0020 on it.
There's more good information he provided. He said the rear axle gear ratio is stamped on the back of the speedometer.
The ratios he provided are 1.54 = 4.08 rear axle ratio; 1.47 = 3.92 rear axle ratio. The 1.54 or 1.47 are the numbers stamped on the back.
The 190 SL speedometer I have has  W=137 on the back which Gernold said is probably a gear ratio but is the wrong one for my car since I have a 4.08 rear axle ratio. He said I could install this replacement in my car but it would show the wrong speed.

Can anyone shed any more light on these speedometers?
What does the 0020 on the front of my speedometer mean?
Anybody interested in a 190 SL speedometer?
Thanks,