Hi,
When downloading the "Alkacon OAMP WebOpt Module 2.0.0" from http://www.alkacon.com/en/modules/downloads/oamp-webopt-2.0.0.html and importing it to my OpenCms - it registers the CSS structured content (like the CSS optimization type) with id 283

While the internal jar contains the class CmsOptimizationCss.java with the constant:
protected static final int RESOURCE_TYPE_CSS = 763;

I ended up downloading from github, generating the jar and zipping the resources folder and importing that.

Thanks