Weirdest egg I've ever seen! (Is it okay?)

[4yearsofchickens]

So awhile back I had this egg from one of my hens, and I thought it was pretty weird...
But I just found this in my chicken run and I'm a little concerned...is my chicken okay? They're all acting okay.. I thought I was pretty read up on chicken stuff but I must have missed something!
Here is the egg:

Hopefully someone can help me I'm a little worried! There appears to be a normal egg inside this weird sac sort of thing. It's kind of leathery looking and feels like sandpaper... And the chunk on the side looks bloody-ish, and is still wet.

 

[Chookchicken]

How old are your hens?

 

[4yearsofchickens]

How old are your hens?

A year old now.. although I have two five year olds, this doesn't look like their eggs.

 

[4yearsofchickens]

I was able to remove the egg, and it looks perfectly normal.. the stuff on the outside was rubbery, and it stank a little too

 

[Chookchicken]

How long have they been laying?

 

[4yearsofchickens]

How long have they been laying?

Since last summer

 

[Dottie the Chicken]

It may be extra membrane? @azygous

 

[Kiki]

What exactly do you feed your flock?

 

[4yearsofchickens]

What exactly do you feed your flock?

The same food I've always fed them, along with occasional scraps, but I'm very picky with them. They hadn't had any scraps for a week.

 

[Eggcessive]

The first egg looks like a slab sided egg. The second looks like an egg within an egg membrane. Those are some of the oddities seen in chicken eggs, and here is a good link to read about the possible causes:
https://www.backyardchickens.com/articles/common-egg-quality-problems.65923/