Unknown Mystery Symbol on Drawing

[E26]

Hello everyone,

I'm having a difficult time figuring out a symbol on an old drawing. The GD&T spec on the drawing is USASI Y14.5-1966 I believe the answer might be in that spec but so far I haven't been able to find any information on it. The symbol is a uppercase D with a tail coming off the top of it and a vertical line in the inside of the D. It is in two places just in front of a surface finish call out. I will post a picture of it and if you think any other information would help you just let me know.

Thanks!

 

[ctopher]

I don't see anything on any specs what that means. Maybe something internal?

ctopher, CSWP
SolidWorks '17
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[E26]

Thanks for the response ctopher, you were correct. It has to do with decarburization control. I was unable to find it previously because the note was crossed out on the drawing. I attached a picture below in case anyone is wondering about it in the future.