Only the code 120lq100 identifies this 48.6 KB PDF, which is filed under schematics with no device, board or revision given. The string appears to be a rectifier part number with a voltage-grade suffix and pairs with a 120lq045 file of the same size, pointing to one family sheet shared across grades. Open it in any PDF reader. Use it to verify ratings and package before replacing a diode, and match the marking on the part rather than trusting the file name alone.
The button opens the matching file on RM Schematics, or a source page if it is not catalogued there yet. The original attachment is from @cyberlanelectonik. Enginerys does not host this file.
How to open a .pdf file
The standard format for schematics, block diagrams, power-sequence charts and service manuals.