The following properties can all be used in a Check-In solution.
Usually, you'll only be needing the standard fields, but for some custom solutions, the special fields can be useful.
Standard fields
client.Name
client.Description
client.RFID
client.RFIDReversed
client.MailDomain
client.Disabled
client.Tags (as list)
client.TagsString (as text)
Special fields
client.EnterpriseData.CustomerNumber
client.EnterpriseData.Organization
client.EnterpriseData.ContactName
client.EnterpriseData.ContactTitle
client.EnterpriseData.TaxNumber
client.EnterpriseData.Address1
client.EnterpriseData.Address2
client.EnterpriseData.PostalCode
client.EnterpriseData.City
client.EnterpriseData.State
client.EnterpriseData.CountryCode
client.EnterpriseData.Email
client.EnterpriseData.Phone
client.EnterpriseData.Mobile
client.EnterpriseData.HasLunchPlan
Group can also be used as a property instead of 'client'.
group.Name
group.ContactName
group.LogoExtension
group.VAT
group.Address1
group.Address2
group.Postal
group.City
group.Region
group.CountryCode
group.Phone
group.Email
group.MailDomain
group.Description
group.CustomerNumber