Brian, I'd venture to guess iron/mineral deposits or rust from hard water???

Very nice machine Brian!   I'm sure you'll enjoy it!

I would guess it's mid-ish (or later?) 70's.  

General Motors sold the Frigidaire Appliances division to WCI in 1979..... so the 1-18 was just a distant memory by 1986 / 87.

BTW... as Nate (Roto204) will attest to, these hold a lot!   Also, as for water level, as odd as it may sound, with the 1-18, "less in more".   You will get better movement (turn/roll-over) if you slightly under-fill it for any given load.

Kevin

That is a late 1970s model WIB or WIG. This was from the last cycle of GM Frigidaire production and could have been manufactured anytime between the fall of 1978 and early 1980 when the Frigidaire name was put on a WCI production machine. 

It has the earlier type "bed-of-nails" lint filter so I don't think it's a "WIB" or "WIG" as both of these had the later pan type. 

Look at the model and serial number sticker. It should be a WC and the serial number should begin by a 6 or 7. This model was made from late 1975 to 1977 as 1976-77 models but it's not older than late 1976 as the lid switch is located under the control panel (earlier models had it under the top behind the rear hinge of the cover). 

If you could post a picture of the serial number, it's right behind the timer at on the angled part at the top of the back cover. 

with a 1-18 !

Lime away is good stuff, be careful of Iron Out on porcelain it will etch it if left too long. 

When I use Iron Out you need a hands on touch with a sponge and plenty of fresh air as  it makes a nasty gas.