Voigtlander rangefinder for accessory shoe

[prinz47]

Good afternoon, I own a rangefinder for accessory shoe made from Voigtlander (this kind of accessory was made from 40' and 60' years). I need to clean the lens inside the apparatus. I tried unscrewing the two front lenses and the accessory shoe slit crews, but I cannot dismantle the external cover. I did not force because the risk to break something inside. There is someone who knows how to do the job and send me please the information I need to dismantle this rangefinder. Thank you very much.