http://www.altejagdwaffen.de/Jagdgeschichte.173.0.html

a No. 1 double gun SN 8929
http://www.rockislandauction.com/viewitem/aid/60/lid/488

"This example has extensive engraving on the receiver and break lever. The left side of the receiver shows a dog pointing at a small gamebird that is taking flight, the right side is engraved with a fox, on the top tang is a bust of a roe deer and the remainder is engraved with oak leaf and acorns. The left side of the receiver is engraved "W. COLLATH" in a banner and the right side is engraved "FRANKFORT A.O." in a banner. The engraver's initials are on the right side between the foxes two back legs. The barrels have had permanent 20 gauge subgauge tubes installed, have a single brass bead sight on the solid rib, are choked .013/.020 and have 2 3/4 inch chambers with an extractor. The bottom flat of the barrels are stamped with a "1" in a circle for Collath's No. 1 horizontal pinfire cartridge which is equivalent to a 12 gauge. Has a safety switch on the top tang along with a brass inlaid initial oval. Mounted on a smooth walnut forearm and beautifully figured checkered walnut pistol grip stock with raised cheekpiece along with a horn trigger guard and buttplate. The underlever is also horn. Length of pull is 14 1/4 inches."

No . 3 double gun SN 16813
http://www.icollector.com/Four-European-...otgun_i18634494

Drilling in No. 1 or No. 4 (not clear to see but given as No. 1)and 9 1/4 x70 SN 10020

http://www.armslist.com/posts/3938025/ev...x-70--drilling-

the single shot gun in 12,5 mm or maybe 32 ga sold by the Dorotheum I had before have the SN 874
https://www.dorotheum.com/en/auctions/cu...age=1&img=0

top lever Drilling in 16 ga and 8x72R SN 17264
http://www.icollector.com/Fine-Early-German-Drilling-by-W-Collath-Sohne_i21575744

Drilling in 9,3x65R SN looks like 20034
https://www.gunsamerica.com/954722874/W-...otgun-Combo.htm

a cal. 1 double gun with "Krüppelschaft" SN 20559

http://www.medwed-hunt.ru/MedwedPosts.aspx?pid=161089&p=1

16 ga double gun W. Collath, Söhne SN 19542
http://www.naturabuy.fr/Vends-ancien-fus...em-2828303.html

double gun in 16 ga(?) or better Cal. 4 SN 7713

http://www.medwed-hunt.ru/MedwedPosts.aspx?pid=198176

when there is anything alright with this pics it looks like original a double gun Cal. 1 SN 12517 now with Cal. 4 barrels SN 13513
http://guns.allzip.org/topic/112/370484.html