"CHECK'' it out ?

[mojjax]

It's a heavy cast iron thing I found in a bottle dump . The markings say -
187 COVER
7.8.9. 10 IN

any ideas ?

[GL]

Cover for an in ground fuel oil tank?
My great grandparents had something similar in their yard when I was a wee laddy.

[al-nm]

used for lots of things some for big hoses some for irrigation pipes some for as said above. uncle had some on his ranch when i was young he used for irrigation.

[bill gent]

toilet seat for little people

[mtntrekr2]

It is a down draft door for the base of a chimney. Mostly used as a
cleanout but main idea is to stop any strong gust of wind from blowing
into the firebox and creating a disaster.
You can also find something very similar on the front of your oil burner
where someone could look inside to "check" the flame.

Just my thoughts
Joe

[NGE]

Toilet seat for hardas$$e$.

[gnewt]

Could it be a meter cover, the cross piece in the inside would interfere with a filling hose?? I could see it used for down draft fuel oil, but a pump would be a problem.
GNewt

[dg39]

Looks like a meter cover to me also. The cross brace rules out a filler of some type.
DG

[fish4walleye]

Looks to be a "check" valve,,used on plumbing so water flows only one direction,,this one was probably on a storm or sewer drain