I've listed my type 1 #6640 Calculator on ebay. It's the model with pin sliders. It's condition is ok, not brilliant as missing 1 pin but still works fine. Here's the link if interested.

http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&item=261004078974#ht_500wt_949

All proceeds to my widowed mother so cut lose with that bidding please!