Rahlfs' Septuagint also translates קָדְשֹׁו as an adjective: ἐν τόπῳ ἁγίῳ αὐτοῦ.
However, there is another LXX textual tradition, preferred by Pietersema in his NET translation, that has a nominal form: ἐν τόπῳ ἁγιάσματος αὐτοῦ.
What is the significance of these two varients?
Is ἁγιάσματος αὐτοῦ a Hebraism, simply translating the Hebrew nominal-construct form while still intending the word to have adjectival force (and thus the same meaning as Rahlfs' ἐν τόπῳ ἁγίῳ αὐτοῦ: his holy place)?
Or does it intend to express something different to the textual tradition found in Rahlfs' Septuaginta, i.e. "holiness" itself, creating the translation: "the place of his holiness"?
If we leave aside the possibility of a Hebraism, our choice between "holiness" and "sanctuary" can have interpretative implications. In LXX Psalm 77:54, for example, we have εἰς ὅριον ἁγιάσματος αὐτοῦ (for Hebrew אֶל־גְּבוּל קָדְשֹׁו in MT Psalm 78:54). In the Hebrew context, it is uncertain whether the mountain in the same verse refers to Zion, Sinai, or something else. The Hebrew simply means "to his holy territory," i.e. translating קדש as an adjective. What is LXX doing with its nominal form ἁγιάσματος? Is it maintaining the ambiguity (i.e. somewhere where God's holiness was present) or is it trying to clarify the referent (to Zion, the territory where his sanctuary is)? If the latter option is to be preferred, we have an example of ancient interpretation.
The same would apply to Psalm 24:3. Is the LXX textual tradition with ἁγιάσματος trying to clarify the referent of מְקוֹם קָדְשֹׁו by using a noun rather than an adjective (i.e. "the place of his sanctuary" rather than "the place of his holiness")?
Another possibility is that rather than ἁγιάσματος being a matter of interpretation (here, clarification), it is just a matter of ancient grammar. Eliezer Berkovits in “The Concept of Holiness” [*] argues that קדש should always be translated as a noun. Perhaps one strand of ancient translation agreed with him. The difference still hasn't been resolved today: some translators MT go for an adjective: "in his holy place" (and thus agree with ἐν τόπῳ ἁγίῳ αὐτοῦ), whereas others (e.g. Seybold) go for a noun: "in his sanctuary" (=ἐν τόπῳ ἁγιάσματος αὐτοῦ).
So what do you think? How ought we translate ἁγιάσματος and what is the significance of its divergence from ἁγίῳ?
Update: In order to strengthen my desire to read ἁγιάσματος as refering to the sanctuary, rather than just holiness per se, J.K. Gayle has kindly pointed out that in 2 Chronicles 36:17 the Hebrew בְּבֵית מִקְדָּשָׁם , which literally means "the house of their sanctuary," is also translated with ἁγιάσματος in the LXX: ἐν οἴκῳ ἁγιάσματος αὐτοῦ (though why it's αὐτοῦ and not αὐτῶν) I'm not sure.
[*] Essential Essays on Judaism. D. Hazony, ed. Jerusalem: Shalem Press, 2002: 247-214. [Originally in his, Man and God; Studies in Biblical Theology, Detroit: Wayne State University Press, 1969].