Welcome! Now that you've asked for the "diving weight", you're officially an IH8MUD member. 
New LC100/LX470 owners aren't until they look under the truck and find that thing and ask about it, as every other user has done before 
Search for "what is this part?", "strange rubber pad" and similar thread titles
It seems to be a damping mass for filtering certain frame vibrations. Users that took it of have reported no noticeable difference. It makes an original paperweigth for the office desk.
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New LC100/LX470 owners aren't until they look under the truck and find that thing and ask about it, as every other user has done before Search for "what is this part?", "strange rubber pad" and similar thread titles
Here's a related thread list
has a Nikon D70 and she needs some help. If the timing were right we would be up for one of your NorCal trips. It would be a great way to combine our two interest.

