I am curious.....
How does your Orthodox Presbyterian Church differ from the PCA, of which I am a member. I was not aware that there was another conservative branch of the Presbyterian Church and am thrilled to see that there is and curious to know about it.
Apple Pan Dowdy, greetings from a PCA neighbor... If my memory serves correctly, there are several sister reformed denominations which share PCA’s key conservative doctrines (in sharp contrast to the PCUSA’s positions). In fact, the PCA spearheads the administration of a joint sponsorship program for military chaplains from the Presbyterian Church in America (PCA), Orthodox Presbyterian Church (OPC), Reformed Presbyterian Church in America (RPCNA), Korean American Presbyterian Church (KAPC) and the Korean Presbyterian Church in America (KPCA). That might be a good indication of their shared beliefs.
The link provided by UncleDick seems to provide a fair distinction. OPC is smaller and more unified than the PCA; and while it is no more conservative than the most conservative presbyteries of the PCA, it is certainly more conservative than the bulk of the PCA. The PCA is more aggressive in church planting, which brings both benefits and negative influences.
The OPC and the PCA are in communion through NAPARC http://www.naparc.org/, along with the ARP (which may be more conservative than the OPC), The Free Reformed Churches of North America, The Heritage Reformed Congregations, The Korean American Presbyterian Church, RCUS, The Reformed Church of Quebec (ERQ), The Reformed Presbyterian Church of North America, and the The United Reformed Churches in North America.