Looks like you got a bit of a bargain there, it appears to be a mid-1960s version, if you let me know the serial number (just the first two letters and the three following numbers if you want to retain some anonymity for it) I can probably be more specific about year and month on manufacture. One thing to be aware of when using this model camera is to always ensure the 'M' and 'X' flash sync setting lever is in the 'X' position before operating the self timer,
or the shutter mechanism will jam permanently! :banghead:
There is reference to this in the instruction manual, which is available in PDF format from Butkus:
http://www.butkus.org/chinon/ To be honest, it's probably best to leave it on the 'X' setting all the time (but it's not difficult to knock the lever and inadvertently move it to 'M'!), and don't use the self timer to be on the safe side!
Personally, I think the 35mm conversion kit is more of a novelty than a necessity, I've used the 35mm kit once in 3 years of owning Yashica 635s, just to see if it worked, which it does... but in portrait format. To shoot in landscape format you have to turn the camera on its side, which makes using a TLR slightly awkward! Besides, as it takes 120 film why would anyone
really want to shoot 35mm in it, unless it was the only camera you had with you and you could only find 35mm film?
If you are still determined to track down and buy a 35mm conversion kit then
make sure all the bits are included. There should be 6 pieces, as per the following photo, plus the leather type case with a separate divider liner/inset. It's quite common to see incomplete kits advertised, so it's a case of buyer beware! I hope this is useful and look forward to seeing some of the photos you take with it.