Corner latch

Hi, I'm looking to replace two corner latches on an old storm window. It looks like there is a number '8' on the 'key' part that attaches to the storm window. On the slide bolt itself it looks like there are some faded numbers. It is hard to make out, but it may say '823' and then '788' in a little circle on the back. I hope this is useful; I am having a hard time finding the correct words to use for describing the parts.
Thank you for your help!