I am working on crafting a focus for an Enchantment. Crafting a focus is an Enchanting + Magic (16 + Object
Resistance, 1 day) Extended Test. What is the objects resistance?

Determine what the telesma (material basis) of the focus is and consult the Object Resistance Table. A necklace made from animal teeth and leather cord, for example, would be a low-tech object with an Object Resistance of 1, while a vibro-knife would be a manufactured high-tech object with an Object Resistance of 3.

What if you're combining something low-tech with something high tech? Say you hand weave a lace sustaining focus, then during the creation of a piece of armour, put it in the plating. Still object resistance one, or goes to 3-5? Lace just being the first thing that pops to mind.

It really depends on what you are enchanting. In the example you gave, the enchantment is going into the lace sustaining focus which is then attached to the armor. The focus is the lace object, not the armor.

Just make sure nothing changes the basic nature of the lace focus during the creation of the armor.

Now if you were combining something simple with something complex and both parts are going into the focus, then you'd have to deal with the highest OR.

Ex: Lace & a machine fabricated medallion. You'd have to overcome the medallion's OR which would be higher than the lace.