"中等光泽装饰" can be translated as "decorative finish with medium gloss" or "medium-gloss decorative treatment" in English.
Here, “装饰” is translated as "decorative" or "decoration" (in the context of a finish or treatment), and “中等光泽” is translated as "medium gloss". The choice between "finish" and "treatment" may depend on the specific context or industry terminology. "Finish" often refers to the final surface quality or appearance of a material, while "treatment" can imply a process or method applied to achieve a certain effect. In this case, either could be appropriate, but "finish" might be slightly more common when describing the visual appearance of a surface.