When was the MacBook Pro Model A1398 built?

Anytime from May 2015 until it was discontinued in June 2018. You really shouldn't be posting your machine's serial number. You can find out certain information regarding your model by keying in your serial number here:

Check Your Service and Support Coverage - Apple Support

Or look on MacTracker's website for more information

919Genesee wrote:

When did it come to market ?

[Edited by Moderator]

That is not the best resource ie 'model number' to identify your Mac....

as you can see from the screenshot below—not so specific.

ref: Identify your MacBook Pro model - Apple Support