These modified suspenders are based on an XL sized, 1967 dated M-1956 Suspenders. The mainly modification is a pair of additional front straps and backpack connectors, seem to be used with M-1945 Field Pack (or its local copy).
Considering those countries/regions who used America made M-1956 LCE and M-1945 Field Pack in the late 1960s, these modified suspenders maybe come from Korea or Taiwan.