Can you provide a picture?
There might be a little red felt "flag" near the bobbin raising button - is that what you're asking about? If so, you can cut your own from a little piece of wool felt - there's info and a pattern for this on pages (2)H-2 and (2)H-3 of this publication:
http://www.tfsr.org/pub/technical_in...obbin_area.pdf
I don't think my 66 has this little felt, but it's been a long time since I had it out. :)
I have seen quite a few machines that have created their own little pads of lint in the feed/bobbin area. If the owner didn't know to remove the needle plate and clean under there, it can really be packed tight with lint and oil - looks just like a piece of felt.