Without pitures there is no way of giving even a rough value. Winchester never made a "presentation grade" at least no in 1948, is it a super grade perhaps? Really we need pictures.
Reelman.
Winchester made special, NON CATALOGUED high grade "presentation rifles" built in it's custom shop throughout it's history.
Many of them were Winchester m70s of all vintages. They were ordered by individuals as gifts to others or for their own collections, and also ordered by the factory management for gifts to dignitaries and as prizes for matches and other special events. Many were made to commemorate production milestones etc.
Were they cataloged items? No, Were they common? no again , but they DO exist. I even bet a few high grade m70s were built in 1948
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As to the engraved Weaver scope, that is less likely due to the thin .drawn steel tubes on Weaver scopes. They really were not thick enough to be hand chiselled. The only "engraved" Weaver scopes I have ever seen are the shallow acid etched "engraved" Weaver 50th Anniversary scopes made in 1983.
In any case, such gun /scope combos are rare and I am sure we would all like to see pics of the OP's prize!