```python
mapping = {
    "2 ohm resistor": "unknown",
    "2 or more gpus": "unknown",
    "2 pac": "unknown",
    "2 plug outlet 20 amp circuit breaker": "unknown",
    "2 pole connectors": "unknown",
    "2 port usb bricks": "unknown",
    "2 powered hubs": "unknown",
    "2 psus": "unknown",
    "2 rig with 3 diablo 1 poclbm kernels": "unknown",
    "2 rig with 4 phatk kernel": "unknown",
    "2 rigs": "unknown",
    "2 rockminers r-boxes": "unknown", # Assuming "rkminer r4-box" but not a direct match.
    "2 shares": "unknown",
    "2 side screws": "unknown",
    "2 terahash miner": "unknown",
    "2 th miner": "unknown",
    "2 th/s bitmine coincraft rig (#ccr-2000)": "unknown",
    "2 titans 2500w": "unknown",
    "2 to 1 usb boards": "unknown",
    "2 units": "unknown",
    "2 windows boxes": "unknown",
    "2 wire 6pin 26in 14 awg power supply cable": "unknown",
    "2 x 1.2 th/s miners": "unknown",
    "2 x 1000watt grid tie true sine wave invertors": "unknown",
    "2 x 120 mm fans": "unknown",
    "2 x 1th/s miner": "unknown",
    "2 x 20gh/s": "unknown",
    "2 x 3.2 th/s miners": "unknown",
    "2 x 5 pin shrouded header (2.54mm)": "unknown",
    "2 x 5970": "5970",
    "2 x 7950s": "7950",
    "2 x batch #3 avalon": "avalon batch 3",
    "2\" rock wool insulation": "unknown",
    "2\"dual\" cables": "unknown",
    "2% extra chips": "unknown",
    "2*6870": "6870",
    "2+th/s bitfury mining equipment": "unknown", # Could refer to Bitfury hardware but not specific.
    "2-5a bench power supply": "unknown",
    "2-chip bitfury 16nm": "unknown", # Likely refers to Bitfury hardware but not specific.
    "2-pin connector": "unknown",
    "2-to-1 pcie cables": "unknown",
    "2-to-1 pcie y-connectors": "unknown",
    "2.0 brother": "unknown",
    "2.0 powered hub": "unknown",
    "2.1a battery pack": "unknown",
    "2.1a supply": "unknown",
    "2.1mm barrel connectors": "unknown",
    "2.2th of fury": "unknown",
    "2.3.4": "unknown",
    "2.3.5": "unknown",
}
```