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							This Japanese Industrial Standard specifies the cylindrical squares made of cast iron and steel to be used mainly for the measurement of perpendicularity.
| Author | JSA | 
|---|---|
| Editor | JSA | 
| Document type | Standard | 
| Format | File | 
| Confirmation date | 2016-10-20 | 
| ICS |  						17.040.01 : Linear and angular measurements in general
						 | 
| Number of pages | 4 | 
| Year | 1970 | 
| Document history | |
| Country | Japan | 
| Keyword | JIS 7539;7539;JIS B 7539-1971 |