There could be a couple of explanations for the 'moving' birth year, hinged primarily on the fact that back then no one really cared how accurately the information was recorded.

First - obviously the decedent doesn't fill out his death certificate. Therefore, the accuracy of the information depends on the knowledge base of the person who filled it out. That's how you can wind up with information that is missing or misleading.

Second - since you don't yet have the DC in hand your information on his age at death is coming from the index. Transcription errors occur all the time, especially when the B-M-D certificates were written out by hand.

Third - The 1900 census is probably the most accurate info since it has the highest liklihood of having come from Matthew and/or Margaret directly. Generally, people know their birthdays...yes, a painfully obvious statement, but it's important to remember that we are talking about a time when DOBs weren't used as an identity tool.

In short, it's not unusual to have these kinds of variations in birth years, particularly when the difference is only a few years. So long as all/most of the other identifying information (address, occupation, family members, etc) match up, you can be reasonably sure that you have the right person.

Hope this helps!

Lynn