Blue glass Carboy of unknown origin - cleaning

I just got a free(cost a bottle of wine) carboy from a friend's customer. Unsure what was in it, And it's different. Kind of a blue glass color, holds about 7 gallons, and has what appears to be threads molded into the glass just below the lip. There are some bubbles in the glass, so it's not the high quality one sees in an Italian carboy, but Seems like it'd be fine for fermenting.

It was rinsed before I got it and I do have it soaking in PBW, but have some concern about any remaining residue that might linger, especially if it was toxic.

Anybody know what these may have been used for? Should I try some other cleaners to make certain everything is gone?

Sounds like a water bottle, with the threaded top. I'd use it but I have little regard for my own well being, in general.

I got one that sounds about like that from the fish lab at my old university about a year ago. Strong bleach for 3 days, strong acid for 3 days, rinse a bunch. Seemed fine, but I traded it to someone else for a 5gal carboy. They're still living and brewing, so I guess everything went ok.

1977Brewer said:

Sounds like a water bottle, with the threaded top. I'd use it but I have little regard for my own well being, in general.

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Definitely NOT used for water. Water has always been 5 gallons, even when glass, AFAIK. This is 7.1 gallons.

bruteforce said:

I got one that sounds about like that from the fish lab at my old university about a year ago. Strong bleach for 3 days, strong acid for 3 days, rinse a bunch. Seemed fine, but I traded it to someone else for a 5gal carboy. They're still living and brewing, so I guess everything went ok.

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I'm pretty sure this was from a lab, too. Starsan is next.

Well, there is some brown stripes on the bottom inside that didn't come out.