Hi PJ, it sounds like you have a valuable old 2 1/2 escudos silver coin from Portugal. The same ship and shield patterns appear on 5 and 10 escudo coins.
2 1/2 ESCUDOS: 0.073 troy ounces silver
5 ESCUDOS: 0.140 troy ounces silver
10 ESCUDOS: 0.336 troy ounces silver
1937 is a good date for the 2 1/2 escudo coin, but you must beware of counterfeits (see below).
DO NOT CLEAN YOUR COIN. CLEANING RUINS VALUE.
Here are approximate catalog values for these coins.
2 1/2 ESCUDOS
worn: $1 US dollar approximate catalog value
average circulated: $5
well preserved: $8
fully uncirculated: $15
2 1/2 escudos dated 1944 and 1951 are very plentiful, cataloging for $2 in well preserved condition
2 1/2 escudos dated before 1942, as well as dated 1948, are more rare, cataloging around $40 in well preserved condition
2 1/2 escudos dated 1937 are very rare, cataloging at $800 in well preserved condition - the are lots of fakes
worn: $3 US dollar approximate catalog value
average circulated: $15
well preserved: $25
fully uncirculated: $50
5 escudos dated after 1946 and also dated 1942 are very common and catalog around $5 in well preserved condition
5 escudos dated 1932 and 1937 catalog at $200 in well preserved condition
worn: $12 US dollar approximate catalog value
average circulated: $25
well preserved: $40
fully uncirculated: $80
10 escudos dated 1932 are quite common, cataloging at $20 in well preserved condition
10 escudos dated 1933 and 1937 catalog around $250 in well preserved condition
10 escudos dated 1942 are rare and catalog at $800 in well preserved condition
As always, one must be careful of counterfeits for valuable collector coins. PJ, you know the history of your coin, and if it could be a fake, it probably is a fake. There are third party numismatic services which will authenticate your coin and assign its numismatic condition for a fee. You might consider one of these. PCGS, NGC, ICG, and ANACS are the recognized services.
About counterfeits, here is a partial quote from an eBay user who has been stuck with counterfeits from China.
'Never EVER ever ever ever ever ever ever ever ever buy coins from a Chinese seller. I don't care how good the coins look in the picture or how good their feedback rating is, just don't do it. I have purchased litterally thousands of dollars worth of Trade Dollars from sellers located in China, sent them off to be graded and had them ALL come back as fake. I have purchased from sellers who claimed their items were Guaranteed 100% Genuine, I've purchased Slabbed Certified Trade Dollars from China and without exception ALL of them, every one has been fake. Even reputable sellers can sell fake Trade Dollars and not even know it. I purchased more than $900 in trade dollars from a reputable seller in the US and sent all the coins off to be graded and EVERY ONE came back from ANACS as 'Not Genuine: Struck Copy.' These coins fooled me as well as the seller who was honest and gave me a complete refund. Stick to PCGS, NGC, ANACS or ICG graded and authenticated coins.'