The following is a list of plans used by Baldwin for 8-18c and 8-18.5c locomotives
Note that the plans are different for each of the classes (but some 8-18c plans are used for 8-18.5c locomotives.)
Plan No's marked in grey are believed to be similar to 8-18c plan 4
Plans used for 8-18c locomotives
Plan No First use Gauge and user notes
1 Apl 1874 3' 3 3/8" (meter guage)
2 Feb 1874 3' 6" guage
3 Aug 1874 3' 1 8/10' guage
4 Aug 1874 3' and meter
5 Aug 1875 Standard or wider gauge
6 Feb 1877 3' 6" guage
7 Aug 1877 4' 7 3/4"
8 Nov 1877 3' 6" guage
9 May 1878 3' , D&RG, Dayton Covington & Toledo, Fulton Co NG, 
10 Jan 1883 3', Fulton Co, 
11 Jan 1884 3' 3 3/8" (meter guage)
12 Dec 1882 standard guage
13 1889 3' gauge, one only, Potomac, Fredricksburg and Pedmont
14 1897 3' 3 3/8" (meter guage)
15 1897 3' 6" guage
16 1906 2' 6"
17 1908 standard gauge
18 1919 3' 3 3/8" (meter guage)
8-18.5c dw8 1895 3' 3 3/8" (meter guage)
Plans used for 8-18.5c locomotives
Plan No First use Gauge and user notes
8-18c dw4 June 1877 3' and meter
1 Oct 1877 3' appears to be an alternate designation of 8-18c plan 4 with larger drivers
8-18c dw1 May 1878 3' 3 3/8" (meter guage)
8-18c dw6 Jan 1879 3'6"
2 Jan 1880 3' D&RG, wagon top boiler
3 Feb 1880 3' gauge, Peter Donahue (SVRR),  Cairo & St Louis, Oregonian, NCO N&C Colusa & Lake, North Georga Improvement, Redondo RR
4 Jan 1882 3' 3 3/8" (meter guage)
5 Mch 1882 3' 6"
6 Jan 1883 3' D&RG, straight boiler
7 Jan 1883 3' 6"
8 Apr 1895 3' 3 3/8" (meter guage)
9 Dec 1896 3'
10  July 1905 3' Lancaster Oxford and Southern