#390 7th Jan 1950, snow logo – Desperate Dan appears with Biffo on the cover. An example in VG sold on eBay UK for £16.05. #440 Xmas issue – snow on logo. Sold for £22.01 in VG/VG condition Apr 2008). #441 New Year 1951 – snow on logo. A complete year 1950 was sold by Comic Book Postal Auctions for £616 in Nov 2009.
These 'special' issues fetch higher values than 'regular' 1950 issues, often twice as much.
#440 is the 13th Christmas issue. Note that these Christmas issues are highly sought after for their covers and fetch easily twice as much as the values for regular issues, often three times.
#400 is dated 18th Mar 1950 - these significant numbers I think would fetch twice the value of a 'regular' issue.