Anti-freeze in windshield washer tank!

Last week while removing some parts in preparation for a full paint I was taking out the windshield/headlight washer tank. When I drained the tank, it was nearly full with what I'm 99% certain was anti-freeze! The car had been stored for over 9 years and I had not even tried to get it running before dismantling for paint. I'm not sure if this was purposeful or accidental but I'm leaning towards the accidental based on other things I've found during the disassemble like a hacked up TB center cover (probably done to try to avoid the TB/WP drill). Anyway, has anyone heard of anti-freeze in the washer tank? Since the 2 filler caps are very close together (although very different in style) I'm wondering if this was just a mistake or an attempt to prevent the washer system from freezing up during storage (unlikely in that it was stored indoors in northern Louisiana).

I wouldn't worry about it. I can't think of any logical reason why someone would intentionally fill it with antifreeze. No harm. Just don't refill it with antifreeze yourself.

I have seen many center TB covers that were hacked up the same way. This is caused by lazy POs and/or incompetent mechanics that are unwilling to move the PS pump and bracket out of the way to properly remove the center cover.