<p>This paper examines collectible design as an emergent hybrid domain at the intersection of art, design, and luxury. Using a two-round Delphi method with expert participants (curators, collectors, designers, and market professionals), we elicited and synthesized judgments in a context marked by ambiguous boundaries and information asymmetries. The study identifies consensus on core value drivers (e.g., authorship, uniqueness, narrative, and aesthetic resonance) and on the central role of expert mediation and field-configuring events in conferring legitimacy. Building on these insights, we introduce <i>symbolic infrastructure</i> as a layered framework (linking evaluative devices, institutional platforms, and identity work) that explains how collectible design stabilizes as a field. The resulting conceptual model specifies directional relationships among category definitions, valuation practices, collector identity, and institutional mechanisms, offering testable propositions for quantitative and mixed-methods research. This paper advances valuation theory, the sociology of cultural markets, and cultural economics by clarifying how novel symbolic fields emerge, structure meaning, and gain legitimacy, while demonstrating the suitability of the Delphi method for theorizing under conditions of limited standardization.</p>