NY -- Standard&Poor's CreditWire 6/25/97 -- Standard&Poor's today has affirmed the ratings of Bank of Nova Scotia and related entities following the bank's announcement that it is seeking to acquire 100% ownership of unrated National Trustco (see list of ratings below). Currently, the bank owns 2.4% of National Trustco's common shares and has commitments from four shareholders to sell Bank of Nova Scotia another 47%. Because Bank of Nova Scotia's offer includes both equity (0.125 of common shares for each National Trustco share tendered) and cash (C$26.475 per share tendered), Bank of Nova Scotia's capitalization will weaken somewhat. However, leverage ratios, particularly Tier 1 capital ratios, will remain within parameters acceptable for the rating. The Tier