Hello, I am a new member from Sweden who recently bought a Dt 175 1975 from France. I've always liked the look of these bikes and when I saw it advertised I couldn't resist buying it. I can't quite figure out the frame number and can't get it to match the numbers that the lists indicate, according to French papers it should be model year 1975. Frame and engine number (the VIN#) CT1 304190.
The tank has no doubt been replaced and doesn't quite fit in the front mounts, but otherwise it looks like a Dt 175 from 74/75 as far as I can see.
Regards
valencia blue

 from near Salisbury, UK.

The main VIN tables here are for US bikes.

See if this listing helps. It says UK, but may well cover Europe as well.

UK VIN Information

Ok, great, thanks, it helped, it seems that my bike are an 1974 model according to this. 
/valencia blue