If the buttons in the bag are really old I doubt there would be any Lucite. Lucite is acrylic which was developed just prior to WWII which would seem "really old" to most folks but by National Button Society standards, "antique" is any button made before 1918. All others are deemed "modern". This has to do with the severe swing in materials availability with the advent of plastic manufacturing and a change in how industry developed and how buttons were made after that year. A push is on to get another age category called "vintage" but we'll see what happens with that. Our society is a good one but changes can be slow to happen. Typically very, very large buttons were a type worn on cloth duster coats in open top roundabout autos. For some reason those coats had HUGE buttons, usually just one or two for easy on and off. The backmarked buttons you mention are some type of synthetic polymer (plastic) but NOT bakelite. Bakelite was not backmarked at anytime and generally was not molded but carved from tubular rods. Anytime you see molding indications (small marks on the side from injection molding, evidence of molding around sewing holes or shank areas), it's probably not bakelite. The only molded bakelite buttons I know of are some the collectors call "realistics". These are buttons with a shape of something real (animal, plant life, people, objects). In the case of these molded realistics, they are very flat with just a slight convex curve which is concave on the reverse side. The top design is sort of an outline type of incised look and when the button is turned over you can see the same incised looking lines but they are reversed. So instead of being raised as they are on the front, they are depressed. You didn't ask about bakelit but I thought I'd throw this in since there seems to be mass confusion out there about what bakelite plastic is and it's currently my pet peeve that just about every older looking plastic gets labeled bakelite. I'd really have to see a sample of your buttons to give you much more information. You can post to this group in the photo area. Once you submit your photo for posting, I just have to approve it. I check back here every few days but if I don't, just e-mail me thru eBay and remind me to get back to the group and do my job. LOL!! -Carol-