From looking around, there seems to be multiple OEM versions of X1600 SE. All have different configuration like DDR or DDR2, 64 bit or 128 bit.
http://www.vgamuseum.info/index.php/cpu/item/793-ati-radeon-x1600-se
I guess this yours:
https://www.tiger-technik.de/Grafikkarten/Grafikkarten-PCI-Express/Sapphire-Radeon-X1600-SE-256M-64Bit-DDR2-PCI-E-VGA-HDTV-DVI-I-Grafikkarte-g342::7220.html ? Just they state its RV516?
In the end, its a big mess and it almost looks like vendors gave names to their cards just like they want. Ive added now X1600 to some RV515 categories so you can just add your results to the following category: https://hwbot.org/hardware/videocard/radeon_x1300x1550x1600_rv515_ddr2_64bit/