As the western world moved away from full power battle rifles such as the H&K G3, FN FAL and M14, Heckler & Koch developed the HK32 and HK33 chambered in 7.62x39mm and 5.56x45mm respectively. Both were based on the G3 design and roller-delayed blowback operating mechanism.
The HK32K. Photo from HKPro.com
While appearing in promotional literature, the HK32 never went into production, or so everyone says.
Wamba, an very observant member of the HKPro.com forum, noticed photos of a Mexican policeman holding what appears to be the HK32.
The photo appeared in this article.
The magazine, both outside appearance and curvature, is significantly different from the HK33.
The receiver also looks slightly different to the SW32, a clone of the HK33 made by Specials Weapons Inc chambered for 7.62x39mm.
I think the most likely explication for these rifles ending up with the Mexican police is that H&K sent pre-production samples to the Mexican Army who manufacture H&K weapons under license and they somehow made their way into the police arsenal.