This is a very nice example I saw at a local show. These were used for fusing electric distribution transformers on their primary side (in their day, typically 1,100 or 2,200 volts). This cutout looks like it was either unused or employed in-service within an indoor installation. By 1930 manufacturers of such switches and fuse cutouts started to use physically similar brown porcelain (boxy) enclosures for this kind of gear. These survived the weather, eventual wood rot and high voltages much better. Porcelain body designs have changed somewhat through the decades however some are still made. Around 1967-1970 the familiar brown porcelain ones were superceded by light gray counterparts. In the 1990s open-type gray porcelain fuse and solid disconnect cutouts were typically the rule with polymer ones the standard today.