This manuscript reports the first example of up-conversion properties involving Yb³⁺ and Tb³⁺ ions in five isostructural Lanthanide-Organic Frameworks (LnOFs), herein designated as UCMarker-1 to UCMarker-5, respectively, and their application as optical probes for the identification of gunshot residues (GSRs) and the ammunition encryption procedure. The excitation of the Yb^{3+ 2}F_7/2 ↔ ²F_5/2 transition (980 nm) at room temperature leads to visible up-conversion (UC) emission of Tb^{3+ 5}D₄ → ⁷F_J. The GSR and lead-free primer residues are easily identified upon UV radiation (λ = 254 nm). These results prove that the exploration of LnOFs to identify GSR is attractive for the identification of ammunition origins or caliber recognition.