I made an error in the cited post by suggesting that there might be some ambiguity between Hunter and Marlin serial numbers for Olympic SBTs. A quick check of serial number ranges indicates that is not true. The Olympic SBT gun was introduced in 1928 in the six digit serial number range; the Marlin '46-'50 serial number range is in no more than five digits. So we can easily distinguish between the two manufacturers.
But a simple question remains with me: How are the serial numbers of the 139 Olympic SBT guns built in 1945-1950 by Marlin prefixed? It doesn't make sense to prefix them with FWS since they are not featherweights. I suppose they are prefixed with the letter S. Is that correct? Does the letter O appear as a suffix on any Olympic SBT or for that matter on the few DBT Olympics that were built?