diff --git a/sbnobj/Common/CRT/CRTPMTMatching.cxx b/sbnobj/Common/CRT/CRTPMTMatching.cxx
new file mode 100644
index 00000000..166561fc
--- /dev/null
+++ b/sbnobj/Common/CRT/CRTPMTMatching.cxx
@@ -0,0 +1,49 @@
+/**
+ * @file   sbnobj/Common/CRTPMTMatching.cxx
+ * @brief  Data product to store CRT PMT Matches (implementation file).
+ * @author Anna Heggestuen (aheggest@colostate.edu) and Francesco Poppi (poppi@bo.infn.it)
+ * @date   November 22, 2024
+ * @see    sbnobj/Common/CRTPMTMatching.hh
+ */
+
+// Library header
+#include "sbnobj/Common/CRT/CRTPMTMatching.hh"
+
+sbn::crt::MatchType sbn::crt::assignFlashClassification(
+  unsigned int topen, unsigned int topex, 
+  unsigned int sideen, unsigned int sideex, 
+  unsigned int bottomen, unsigned int bottomex
+)
+{
+  MatchType flashType;
+  if (topen == 0 && sideen == 0 && topex == 0 && sideex == 0){
+    if(bottomex==0 && bottomen==0) flashType = MatchType::noMatch;
+    else if (bottomex>=1 && bottomen==0) flashType = MatchType::exBottom;
+    else if (bottomex==0 && bottomen>=1) flashType = MatchType::enBottom;
+    else flashType = MatchType::others;
+  }
+  else if (topen == 1 && sideen == 0 && topex == 0 && sideex == 0){
+    if(bottomex==1 && bottomen==0) flashType = MatchType::enTop_exBottom;
+    else flashType = MatchType::enTop;
+  }
+  else if (topen == 0 && sideen == 1 && topex == 0 && sideex == 0)
+    if(bottomex==1 && bottomen==0) flashType = MatchType::enSide_exBottom;
+    else flashType = MatchType::enSide;
+  else if (topen == 1 && sideen == 0 && topex == 0 && sideex == 1)
+    flashType = MatchType::enTop_exSide;
+  else if (topen == 0 && sideen == 0 && topex == 1 && sideex == 0){
+    if(bottomex==0 && bottomen==1) flashType = MatchType::exTop_enBottom;
+    else flashType = MatchType::exTop;
+  }
+  else if (topen == 0 && sideen == 0 && topex == 0 && sideex == 1)
+    if(bottomex==0 && bottomen==1) flashType = MatchType::exSide_enBottom;
+    else flashType = MatchType::exSide;
+  else if (topen >= 1 && sideen == 0 && topex == 0 && sideex == 0) // could also add `if (MatchBottomCRT)` here
+    flashType = MatchType::enTop_mult; 
+  else if (topen >= 1 && sideen == 0 && topex == 0 && sideex >= 1) // and here 
+    flashType = MatchType::enTop_exSide_mult;
+  else
+    flashType = MatchType::others;
+  return flashType;
+
+}
diff --git a/sbnobj/Common/CRT/CRTPMTMatching.hh b/sbnobj/Common/CRT/CRTPMTMatching.hh
index e1eb62c9..2c2b336a 100644
--- a/sbnobj/Common/CRT/CRTPMTMatching.hh
+++ b/sbnobj/Common/CRT/CRTPMTMatching.hh
@@ -5,8 +5,8 @@
  * @date   June 1 2023.
  */
 
-#ifndef CRTPMTMATCHING_hh_
-#define CRTPMTMATCHING_hh_
+#ifndef SBNOBJ_COMMON_CRTPMTMATCHING_HH
+#define SBNOBJ_COMMON_CRTPMTMATCHING_HH
 
 // C++ includes
 #include <vector>
@@ -33,6 +33,22 @@ namespace sbn::crt {
       exSide_enBottom   = 14, ///< Matched with one Bottom CRT hit before the optical flash and matched with one Side CRT hit after the optical flash.
       others            = 9  ///< All the other cases.
       };
+
+  /**
+   * @brief Returns the classification of a TPC object based on the CRT hits associated to it.
+   * @param topen number of hits on the top CRT earlier than the object (entering)
+   * @param topex number of hits on the top CRT later than the object (exiting)
+   * @param sideen number of hits on any side CRT earlier than the object (entering)
+   * @param sideex number of hits on any side CRT later than the object (exiting)
+   * @param bottomen number of hits on the bottom CRT earlier than the object (entering)
+   * @param bottomex number of hits on the bottom side CRT later than the object (exiting)
+   * @return a value encoding the classification of the TPC object
+   *   
+   */
+  MatchType assignFlashClassification(unsigned int topen, unsigned int topex, 
+				      unsigned int sideen, unsigned int sideex, 
+				      unsigned int bottomen, unsigned int bottomex);
+
   /// Information about a CRT hit matched with a PMT flash.
   struct MatchedCRT {