What size screw is used to hold the decapod tender floor to the body (ID = 10159)
Look on the parts diagram in the online Ho parts store
The parts diagrams and parts store do not list the actual size or threads for any screws. They only give the part number. This one seems to be in stock:
https://estore.bachmanntrains.com/index.php?main_page=product_info&cPath=68_630&products_id=7275
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