There are several Challenge Caches that require you to find the oldest cache in a certain number of countries, hopefully this list will be useful in your quest. We will try and keep the list up to date.
Scotland GCF0 Scotland’s First Traditional 15.12.2000
England GC171 View from Coombe Hill Traditional 14.1.2001
Wales GC2BA First in Wales Traditional 17.2.2001
Northern Ireland GC38D7 pussycat Traditional 10.2.2002
Andorra GC42E3 Casamanya Traditional 16.3.2002
Antigua and Barbuda GC5D78 Lookout Point Virtual 8.5.2002
Austria GC1298 Salzig Hund Traditional 23.7.2001
Australia GC3E Lane Cove Virtual 18.5.2000
Belarus GC1V5WY The Second in Belarus 24.6.2009
Belgium GC40 Geocache Traditional 7.7.2000
Bermuda GC4B5C Deliverance Virtual 9.4.2002
Bosnia and Herzegovina GCJVHV Bukovic Mountain #1 Traditional 12.6.2004
Brazil GCC67 Mission 4: Southern Bowl Ape 14.6.2001
Bulgaria GCB088 The Orpheus Cache Traditional 30.11.2002
Canada GCBBA Geocache—Canada’s 1st geocache Traditional 28.6.2000
China GC201F Berry Virtual Cache Virtual 2.10.2001
Croatia GC2499 Saint Ivan Traditional 25.10.2001
Cuba GC5B6F Cuba Libre Traditional 18.5.2002
Cyprus GC926F The first traditional in Cyprus Traditional 21.9.2002 18.8.2001
Czechia GCE50 Tex-Czech Traditional 1.6.2001
Denmark GC6A Kippers in the Jungle (Denmark’s first) Traditional 20.9.2000
Estonia GC263 HE-stash / HE-aare Traditional 10.2.2001
Faroe Islands GCMPFC Skansin Traditional 5.2.2005
France GC7A2 La Vigie Traditional 22.4.2001
Finland GC72 Sun Gear Traditional 30.9.2000
Germany GC26C Medieval View Traditional 11.2.2001
Gibraltar GCA227 1st Gibraltar Traditional 28.10.2002
Greece GC1B5B Agia Irene Traditional 18.8.2001
Greenland GC8074 El Conquistador’s Treasure Traditional 11.8.2002
Guernsey GC3209 View.1 Traditional 13.1.2002
Hungary GCD68 FakeCastle 24.6.2001
Iceland GC7AD7 Karin Near Kistufell Traditional 5.8.2002
Ireland GC43 Europe’s First Traditional 3.6.2000
Isle of Man GC5A4C Manx Traditional 20.5.2002
Italy GC17B3 Bergwind 15.5.2001
Japan GC268C Oku Hamanako Traditional 14.11.2001
Jersey GCB662 Jersey number One Traditional 15.12.2002
Kenya GC53 Rift Valley Virtual 15.6.2000
Latvia GC1J94K Trebas 3 litru burka Traditional 14.6.2003
Liechtenstein GCC2F4 Liechtenstein’s First Traditional 12.1.2003
Luxembourg GC503C BurGeo 2 Traditional 21.4.2002
Macedonia GCB82C Tupolev 154 Traditional 23.12.2003
Malta GCHEQ7 The Ring of Clapham Junction Traditional 4.1.2004
Malaysia GC9FDB Welcome to KL Virtual 24.10.2002
Mauritius GCH02Z Garden Treasure Traditional 22.9.2003
Moldova GCT1QN First Cache in Moldova Traditional 16.1.2006
Monaco GC2DC2 top of monaco Traditional 24.12.2001
Montenegro GC1095F Dome View 4.1.2007
Netherlands GC198 Amsterdam Urban 1 Traditional 21.1.2001
New Zealand GC46 Geocache by Kevin Anderson (Wellington) Traditional 26.5.2000
Norway GCBBF Norges første, I Bergen, The first cache in Norway Multi 9.6.2001
Poland GC26A9 Ndebele Virtual 1.11.2001
Portugal GC8EF9 AZGTJ – Translant Chess Cache Traditional 15.5.2001
Romania GC5D8 Dracula’s Castle Traditional 1.4.2001
Russia GC162E Mutnovsky:1 (Nikolay Kam:2) Traditional 12.8.2001
San Marino GCNTKF [BAU] San Marino #1 Traditional 5.5.2005
Slovakia GCKRD6 Mokre nohy (Wet Legs) Mystery 6.7.2001
Slovenia GC103E Prvi Geocache v Sloveniji Traditional 29.6.2001
South Africa GC185 Sentinel View Traditional 18.1.2001
Sweden GC4D Match Stash Traditional 11.8.2000
Switzerland GC2A5 Gstaash Traditional 27.1.2001
Ukraine GC11WCJ Verecke pass (GC896 – Honglalás) Traditional 25.7.2005
USA GC30 Mingo Traditional 11.5.2000