Granite stela of Peribsen
From Abydos, Egypt, 2nd Dynasty, around 2800 BCE
Height: 113.500 cm, width: 33.000 cm
Gift of the Egypt Exploration Society EA 35597
© Trustees of the British Museum

This is "One of a pair which stood at the entrance to the king's tomb". Petrie's Royal Tombs of the Earliest Dynasties has a photo of both the steles:

Some more illustrations of Peribsen's artifacts have come to light.

The above is a stone vase of Set-Peribsen with the inscription "tribute of the people of Sethroë", National Archaeological Museum of France (Musee des Antiquites Nationales, St Germain en Laye.) (Source: Wikipedia, photographer "Iry-Hor")

Line detail I created from above photo....

How the name of Set is referred to in the "people of Sethroë"

There's another drawing based on a porphyry-vase displaying the serekh of Peribsen; note the Set-animal with a sun-disk above it:

My refining of a PNG after a SVG by Andel, original After Hermann Alexander Schlögl: Das Alte Ägypten. S.77ff.

Porphyry is "a hard igneous rock containing crystals, usually of feldspar, in a fine-grained, typically reddish groundmass," from Google search result, based on the Oxford English Dictionary. There's at least one other instance of Set being associated with Ra, here featuring Merenptah offering to Set, who is depicted with the Solar Disc.

The museum website is claiming the standing figure in the seal below is the god Ash, but is it Set wearing the white crown, as the figure definitely has a pronounced snout?

Fragment of clay jar-seal from the tomb of Peribsen, Abydos
Second Dynasty, about 2800 BCE. British Museum #EA 35595
This seal bears the name of Peribsen with the Set-animal. Another seal, #EA 35596, at the British museum bears his earlier name Sekhimib, with the falcon of Horus.
Photo credit © Heidi Kontkanen

Petrie's "Royal Tombs" features a line drawing of a similar seal of Peribsen showing a snouted deity wearing the tall white crown:

TeVelde clarifies this mystery:
"Since the reign of Peribsen, the Libyan god Ash can be depicted with the head of Seth, as well as with a human head or a falcon's heas. We see then that a considerable time before the N.K. Ash, the foreign god, could be conceived as a form of revelation of Seth, the lord of foreign countries." (Seth, God of Confusion: A Study of His Role in Egyptian Mythology and Religion, by H. Te Velde, page 114)

Let's have a closer look at Peribsen's name:

"So far as could be checked, only one king took a separate Seth name besides his Horus name. This happened in the 2nd dynasty. The Horus name of this king was Sekhemib and his Seth name was Peribsen. We are justified in calling it a Seth name, because the Seth-animal is depicted over the serekh, instead of the usual Horus falcon." 1

All the translations I've seen of Peribsen’s name are making a "pri" out of a "per". "Per" means "house, palace, seat of government"2. "Pri" means "go, come out, be reknowned, burst forth, go up, ascend", via Faulkner (via Cintron)3. TeVelde's Garnot seems to take the 'pri' as perhaps to 'come out' and be 'revealed', for as translated from the French, I get “The desires of both are revealed.”4 But what if the 'per' is really a 'per'? To say of the king that he is “the house of their desires” is to say that the two gods DWELL within him, and thus their hearts, their desires are within him. I think this is closer to what the ancients meant. Not only that, as we examine the hieroglyphs in Faulkner's Dictionary , we see 'Pri' is formed of three glyphs, not just the 'per' glyph, but also the 'ren' glyph and the 'walking feet', which are not in Peribsen's name.5

1. Herman Te Velde, Seth, God of Confusion: A Study of His Role in Egyptian Mythology and Religion, trans. Mrs. G. E. van Baaren-Pape, (Leiden, E.J. Brill, 1977), 72.
2. E. A. Wallis Budge, An Egyptian Hieroglyphic Dictionary in Two Volumes, Vol. 1, (Dover Publications, 1978, adapted from the original John Murray London, 1920), 237.
3. Raymond Faulkner, as quoted in David Cintron, Study of 2nd Dynasty Seth Names (2001), (Dec. 16, 2011)
4. "leurs sentiments (leurs désirs) à tous deux se révèlent," Te Velde, 73.
5. Raymond O. Faulkner, A Concise Dictionary of Middle Egyptian, (Griffith Institute Ashmolean Museum, Oxford, 1981), 90.