For symmetricom S200, S250 or S100, S300 S350 use, no need to tear down the motherboard, no need to solder the pin of OCXO or other resistor (also no need to consider the empty OCXO position exists or not for S3xx, S100), just plug into P3, short the Jumper JP3; 89 - 99 USD
https://www.ebay.com/itm/406912136786