It looks like the case is textured. Many prototypes don't have a textured case, although there are varying cases within prototypes based on which stage they are in.
Most everyone knows about the clear-case SE prototype. There exists an earlier prototype of the SE, which is beige, has no texture to its case, has no port icons (another telltale sign), has a Mac Plus brightness knob, and has a serial number indicating November 1986 as its date. (The serial sticker appears to be hand-made on a printer). I know of at least two of these still in existence (one of them is mine and is believed to have been sent to Carnegie Mellon University in Pittsburgh for testing at one point). To my knowledge, these were earlier than the clear case SE.
There is an LC Prototype that has been on-and-off eBay for the better part of the past year. It has a June 19, 1990 date on the chips. The case has texture and port icons. Also, note the serial number and date sticker on the power supply.
https://www.ebay.com/itm/Apple-Macintosh-LC-PROTOTYPE-Mac-Elsie-Classic-68020/223474905192?hash=item3408247068:g:OBsAAOSw7adahSa0
I can only hope they pulled the Maxell from it!!