Adding magic to masterwork armor...just to confirm...

[Prethen]

I can buy Full Plate Mail and make it as masterwork at the time of purchase and delay adding a "+1" enhancement for later correct? It doesn't appear you can delay adding masterwork to it, but I believe magical enhancements can be added over a period of time.

[Archaeik]

Masterwork Transformation

Otherwise, yes MW must be added at creation.

And yes, you can wait to add magical properties.

[Prethen]

Ah, interesting about the spell possibility. Thank you.