Vintage small hole key

Need a trunk lock and key for trunk. I have never given any thought about the small hole key? I haven’t gone around and checked to see what type of key my cars have. Would someone want to give me the lowdown this small hole key business. Thanks

Small hole lock set as original:

Lock set on eBay

Big hole keys as used in the mid 1970’s - and later:

Big hole lock set on eBay