Doors and Windows - Is it exterior or?? if so, what do I do to finish it?

My hubby and I bought a door at a yard sale for a build product company (doors, windows, decking etc). We got a French door, with 15 glass panes. It didn't come with anything, like instructions or even any packing materials around it. The idea was to finish it as an stained and weatherproof front door for our house. Now, our concern is "Is it really an exterior door?" How can I tell? I was told to look for two panes of glass but with the plastic film on the panes I cant tell but it does say tempered. Does that mean it is or are all glass doors tempered? According to the makers website (it had a made by sticker on it) is says its a solid core door and the exterior version would be a insulated tempered glass door. I don't want to take the film off because he will be staining and clear coating.

Is there any other way to confirm exterior? (I will have hubby look at the glass and see if he can tell.)
AND
If I can use it as a front door. What's the best products to use? I know to put a wood conditioner on first and then either a stain or 2 in 1 stain on and then several coats of polyurethane on top of that.
The door is in a fairly sheltered area, under a overhang and out of most direct sunlight but it is an outside door so still needs to be able to stand up to Maryland weather.
I see that Sherwin Williams is having a sale this weekend (isn't everybody?) and hopefully we can get there or ?? Lowes? Home Depot?
Any suggestions????

Oh, I will also be putting curtins on the inside if that makes any differance? Probley will use insulated in the winter and lighter ones in summer.
Thanks in advance,
Willa

Welcome to the forums Willa

An exterior wood door is a little thicker than an interior door. Insulated glass is also thicker [2 panes w/gap in between]

Generally SWP has better coatings than a big box but with stain and poly you should be ok buying minwax at the big box for a lesser price than the paint store will charge. Use minwax's helmsman spar urathane on the outside of the door.Don't forget to seal the top and bottom of the door!

exterior door is 1 3/4, interior is 1 3/8. If it is to be an exterior door, it should have insulated glass. Exterior will likely have 3 -4" hinges, interior, 2-3 -3 1/2" hinges.

Hubby looked at it tonight, single pane, 1 3/8 inch. Dern it.
So, Is there any possibly of salvaging it to use as a front door? We're a low/no crime rural area, the doorway is shaded and recessed and I'll put insulated curtins on the inside... I'm grasping at straws here, Its so pretty! What if we put a glass screen door in front on it?

Or anyone want to buy a interior 15 pane pine french door???

Interior doors are not designed or weatherstripped to be air tight. And to make them so can be difficult. Unless you live in the sun belt, you may not like those doors when the cold winds come calling.

I have used an interior door a time or two on the exterior but it isn't a good idea. The more it is protected from the elements the longer it will last. The paint/poly must be kept in good shape! A storm door should help it to last. It won't be as secure or weather tight as a door designed for exterior use.

Because the door is thinner you may need to make allowances for the thickness difference when installing. Does the french door have hinges or the mortice to set them in? Will the existing door's hinges fit the new door? It won't be a simple door swap.

Thank you both for your thoughts! The current door is just your average metal door. We had added a wooden screen door before but it got broken. The french door is just a slab (is that the correct term?) No hardware or pre made holes so we have a fresh slate with that and it will fit the current door and we can resue the hinges. We do want to get a new lock set but again no holes in the door so we can match it to the current ones. We're thinking about getting one of thoes full view locking glass storm doors with a screen. Hopefully if we install that and be sure to weatherstrip extra well it will be ok. I'll add extra coats of the poly and seal every edge super good.
IF we decide to do it. Not sure yet. LOL, We only paid 100 for the door so we could always resell it if its not going to work. Guess I'll see what we can find this weekend as fr as storm doors go.