The 400G QSFP-DD optical Xcvr module QDD-400G-ZR-M-HP (Part Number: 740-131168) may be displayed as UNKNOWN in the output of "show chassis hardware".

root@mx304> show chassis hardware | no-more 
Nov 29 10:32:52
Hardware inventory:
Item             Version  Part number  Serial number     Description
Chassis                                HB973             JNP304 [MX304]
Routing Engine 0 REV 18   750-123749   BCFH1995          RE 2700 8C 128G
CB 0             REV 41   750-123404   BCFH9282          Control Board
FPC 0                     BUILTIN      BUILTIN           FPC-BUILTIN
  CPU            REV 13   750-122877   BCFJ4309          JNP304 PMB
  PIC 0          REV 30   750-122718   BCFH3027          MRATE LMIC 16x100G/4x400G
    Xcvr 0       REV 01   740-061409   1W1CQAA8500X7     QSFP-100GBASE-LR4-T2
    Xcvr 1       REV 01   740-061409   1W1CQAA8501QY     QSFP-100GBASE-LR4-T2
    Xcvr 14      REV 01   740-131168   1T1TZUA90201P     UNKNOWN <<<<<<<<<<<<<<<<<<<< QDD-400G-ZR-M-HP optical Xcvr
  PIC 1          REV 30   750-122718   BCFH8481          MRATE LMIC 16x100G/4x400G
    Xcvr 14      REV 01   740-096176   1G1TZHA90101U     QSFP56-DD-400GBASE-LR4-10
PEM 0            REV 02   740-110420   1F28D160317       DC AFO 2200W Power Supply
PEM 1            REV 02   740-110420   1F28D160242       DC AFO 2200W Power Supply
Fan Tray 0       REV 08   760-126744   BCFJ9334          JNP304 Fan Tray, Front to Back Airflow
Fan Tray 1       REV 08   760-126744   BCFJ9333          JNP304 Fan Tray, Front to Back Airflow
Fan Tray 2       REV 08   760-126744   BCFJ9305          JNP304 Fan Tray, Front to Back Airflow
SFB 0            REV 13   750-122847   BCFC3935          Switch Fabric Board
TIB              REV 09   750-126514   BCFF6043          Timing Interface Board

The Xcvr model QDD-400G-ZR-M-HP (Part Number: 740-131168) is supported on MX304 from Junos 23.4R1. On Junos versions older than 23.4R1, this optic is not recognised, and is displayed as UNKNOWN.

Ref. https://apps.juniper.net/hct/model/?component=QDD-400G-ZR-M-HP&tab=oView

Case # 2024-1128-325422