The fuÞark rune URUZ

The fuÞark rune URUZ
Elmer Antonsen submitted a paper at the First Runic Symposium, reviewing the conflict between 19th-century German & Scandinavian nationalists over the phonetic value of the algiz rune as it appears in inscriptions in the Schleswig-Holstein region. It seems that the Germans main arguments over the inscriptions is that they were in proto-Germanic, so algiz represented z. The Scandinavians countered that the inhabitants of the region were already speaking proto-Norse when the inscriptions were carved, so algiz really represented r. Although Prussia forcibly annexed Schleswig-Holstein, the Scandinavian linguists carried the argument, and to this day algiz is usually transcribed as R The problem is, according to Antonsen, the phonetic value of the rune really is z. This is why some contemporary runologists transcribe algiz as R, but assign it a phonetic value of z in their translations of inscription.

See: Elmer H Antonsen, "Linguistics and Politics in the 19th Century:
The Case of the 15th Rune," Michigan Germanic Studies, vol. 6, pp. 1-
16 (1980).
 
The runes of the 24 letter fuÞark occur in a number of varieties (see Arntz 1944, 65-72) determined by the chronological period, the geographic area, the substance from which they are carved & perhaps also the school to which the rune carver belonged to, as well by personal idiosyncrasies. In many instances, we have only a vague notion of which shape was original for any given rune. Following on from this notion, the phonological values of most of the runes can be established with great certainty on the basis of their use with identifiable words, of comparative linguistic evidence, or of their correspondences to letters in the Mediterranean alphabets (Marstrander 1928, Hammerstrom 1930, Arntz 1944, 30-64, Krause 1970 § 21 – 9) and of the rune names recorded in the medieval manuscripts (Arntz 1944, 167 -233, Düwel 1968, 107 - 8, Krause 1970, § 15 - 20)

But it was not until the latter half of the 19th century that algiz at the end of RUNAR (meaning runes) was recognised as corresponding to z alternating with s in Gothic (Bugge 1865, Wimmer 1867, 32  4) and therefore the reflex of Proto Indo European (PIE). So depending on the timeline or the school of thought from which the sound values may have developed would give you an approximate answer to the enigma  but as a best guess in this instance would be to use yr at the end. Interestingly the original form of uruz iinside its original form is that of an inversed V